Conductive film coated substrate, multilayer reflective film coated substrate, reflective mask blank, reflective mask, and semiconductor device manufacturing method

ABSTRACT

Provided is a conductive film coated substrate, including a conductive film formed thereon. In a relationship between a bearing area (%) and a bearing depth (nm) that are obtained by measuring, with an atomic force microscope, a region of 1 μm×1 μm of a surface of the conductive film, the surface of the conductive film satisfies a relationship that (BA 70 −BA 30 )/(BD 70 −BD 30 ) is 15 or more and 260 or less (%/nm), and a maximum height (Rmax) is 1.3 nm or more and 15 nm or less.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2014/07499 filed Sep. 22, 2014, claiming priority based onJapanese Patent Application No. 2013-202494 filed Sep. 27, 2013, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

This invention relates to a conductive film coated substrate, amultilayer reflective film coated substrate, a reflective mask blank,and a reflective mask that are for use in EUV lithography, and to asemiconductor device manufacturing method using the same.

BACKGROUND ART

In recent years, in a semiconductor industry, as a semiconductor devicebecomes more integrated, a finer pattern over a transfer limit ofrelated-art photolithography using ultraviolet light becomes necessary.EUV lithography, which is an exposure technology using extreme ultraviolet (hereinafter referred to as “EUV”) light, is promising forenabling formation of such a fine pattern. In this case, EUV light meanslight in a wavelength band of a soft X-ray region or a vacuumultraviolet radiation region, and specifically, light at a wavelength ofabout 0.2 nm to about 100 nm. As a mask for transfer used in this EUVlithography, a reflective mask is proposed. Such a reflective mask is amask in which a multilayer reflective film for reflecting exposure lightis formed on a substrate and an absorber film for absorbing exposurelight is formed on the multilayer reflective film in a pattern.

The reflective mask is manufactured by forming an absorber film patternby photolithography or the like from a reflective mask blank including asubstrate, a multilayer reflective film formed on the substrate, and anabsorber film formed on the multilayer reflective film.

In general, the multilayer reflective film and the absorber layer areformed using a film forming method such as sputtering. In the filmformation, the substrate for the reflective mask blank is supported in afilm forming apparatus by support means. As the support means for thesubstrate, an electrostatic chuck is used. Therefore, in order tofacilitate fixing of the substrate by the electrostatic chuck, aconductive film (back surface conductive film) is formed on a backsurface of an insulating substrate for the reflective mask blank such asa glass substrate.

As an example of the conductive film coated substrate, in PatentDocument 1, there is disclosed a conductive film coated substrate foruse in manufacturing a reflective mask blank for EUV lithography, whichhas a feature in that the conductive film contains chromium (Cr) andnitrogen (N), an average concentration of N in the conductive film is0.1 at % or more and less than 40 at %, a crystal state of at least asurface of the conductive film is amorphous, a surface roughness (rms)of the conductive film is 0.5 nm or less, and the conductive film is acomposition gradient film in which the N concentration in the conductivefilm changes along a thickness direction of the conductive film so thatthe N concentration on the substrate side is low and the N concentrationon the surface side is high.

Further, in Patent Document 2, there is disclosed a conductive filmcoated substrate for use in manufacturing a reflective mask blank forEUV lithography, the conductive film being formed on the substrate,which has a feature in that the conductive film includes at least twolayers of a layer formed on the substrate side (lower layer) and a layerformed on the lower layer (upper layer), the lower layer of theconductive film contains chromium (Cr), oxygen (O), and hydrogen (H),and the upper layer of the conductive film contains chromium (Cr),nitrogen (N), and hydrogen (H). Further, in Patent Document 2, it isdisclosed that a surface roughness (rms) of the conductive film is 0.5nm or less.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP-B-4978626

Patent Document 2: WO 2012/105698 A1

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

As a pattern in lithography using EUV (Extreme Ultra-Violet) becomesrapidly finer, a defect size of an EUV mask that is a reflective maskbecomes smaller year after year. In order to find such a fine defect, aninspection light source wavelength used in defect inspection isapproaching a light source wavelength of exposure light.

For example, as a defect inspection apparatus for an EUV mask, areflective mask blank serving as a master thereof, a multilayerreflective film coated substrate, and a substrate for a mask blank,highly sensitive defect inspection apparatus having an inspection lightsource wavelength of 266 nm (for example, an EUV exposure masksubstrates/blanks defect inspection apparatus “MAGICS M7360”manufactured by Lasertec Corporation), 193 nm (EUV mask/blank defectinspection apparatus “Teron 600 series” manufactured by KLA-TencorCorporation, for example, “Teron 610”), and 13.5 nm are widespread orproposed.

Incidentally, a fiducial mark can be formed on a substrate for a maskblank, a multilayer reflective film coated substrate, and a reflectivemask blank (collectively referred to simply as “substrate and thelike”), and positions of the fiducial mark and of a defect detected bythe defect inspection apparatus can be controlled based on coordinatesthereof. Based on positional information of the defect (defect data)obtained, drawing data for manufacture of the reflective mask iscorrected so that an absorber pattern is formed at a location where thedefect exists based on the defect data and transferred pattern (circuitpattern) data, thereby being able to reduce defects. Therefore, in orderto reduce detects, it is important to accurately measure a position of adefect.

When an object to be inspected such as a reflective mask, a reflectivemask blank, and a multilayer reflective film coated substrate isinspected for a defect by a defect inspection apparatus, it is a commonpractice to mount a conductive film formed on a back surface of thesubstrate and the like (back surface conductive film) of such an objectto be inspected on a mount provided on a stage of the defect inspectionapparatus and fix the object to be inspected to the stage. The inventorsof this invention found that the fixing of the substrate and the like onthe stage was not reliable, and that, due to slippage of the substrateand the like when the stage of the defect inspection apparatus wasmoved, positional accuracy of detecting a defect by the defectinspection apparatus was sometimes lowered.

Further, the inventors of this invention also found that, in addition tothe case of the positional accuracy in defect detection, whencoordinates of a fiducial mark formed on a reflective mask blank or amultilayer reflective film coated substrate were measured by acoordinate measuring machine, and when a desired transfer pattern wasmeasured before or after the pattern was formed on a reflective mask,and other such cases, the fixing of the substrate and the like by amount on which the back surface conductive film was mounted was notreliable and a problem of lowered positional accuracy arose due toslippage of the substrate and the like when a stage of the coordinatemeasuring machine was moved.

While the problem of lowered positional accuracy as described abovearises, if the surface smoothness of the back surface conductive film isnot satisfactory, an apparent defect (pseudo defect) may be a problemwhen the back surface conductive film is inspected for a defect by adefect inspection apparatus. Specifically, a problem arises that, due tohigh detection sensitivity of the defect inspection apparatus, when aback surface conductive film is inspected for a defect, the number ofdetected defects ((the number of detected defects)=(the number ofcritical defects)+(the number of pseudo defects)) becomes larger than anactual number, and, in some cases, defect inspection becomes impossible.

A pseudo defect as used herein means one which is erroneously determinedto be a defect in inspection by a defect inspection apparatus, and isliable to occur when a surface to be inspected is rough.

Accordingly, an object of this invention is to provide a conductive filmcoated substrate, a multilayer reflective film coated substrate, areflective mask blank, and a reflective mask with which, when thereflective mask, the reflective mask blank, and the multilayerreflective film coated substrate are inspected for a defect by a defectinspection apparatus, and, when coordinates of a fiducial mark formed onthe reflective mask blank and the multilayer reflective film coatedsubstrate and of a transfer pattern of the reflective mask are measuredby a coordinate measuring machine or the like, the positional accuracyof a defect detected by the defect inspection apparatus and thepositional accuracy of the fiducial mark, the positional accuracy of thetransfer pattern by the coordinate measuring machine, and the like canbe improved. Specifically, an object of this invention is to provide areflective mask, a reflective mask blank, and a multilayer reflectivefilm coated substrate which can, when the reflective mask, thereflective mask blank, and the multilayer reflective film coatedsubstrate are inspected/measured by a defect inspection apparatus, acoordinate measuring machine, and the like, inhibit slippage of a backsurface conductive film when the substrate and the like are fixed by amount. Another object of this invention is to provide a reflective maskblank and a multilayer reflective film coated substrate which can, atthat time, inhibit detection of a pseudo defect due to surface roughnessof the back surface conductive film and facilitate finding of a criticaldefect such as a foreign matter or a flaw.

Means to Solve the Problem

As a result of diligent review for the purpose of solving the problemdescribed above, the inventors of this invention found a correlationbetween lowered positional accuracy of a detected defect or loweredpositional accuracy of a pattern (such as a fiducial mark or a transferpattern) determined by measuring the coordinates, and the surfaceroughness of the back surface conductive film. The inventors of thisinvention further found that, when the surface of the back surfaceconductive film had a predetermined surface geometry, the positionalaccuracy of a defect detected by a defect inspection apparatus and theaccuracy of measurement of the pattern by the coordinate measuringmachine were enhanced, to thereby reach this invention. Specifically,the inventors of this invention found that, in order to enhance thepositional accuracy of a defect detected by a defect inspectionapparatus and the positional accuracy of a pattern determined by acoordinate measuring machine, it was necessary to inhibit slippage ofthe back surface conductive film when the substrate and the like werefixed by the mount. The inventors of this invention further found that,in order to inhibit the slippage of the back surface conductive film andto inhibit detection of a pseudo defect due to surface roughness of theback surface conductive film, it was necessary that the relationshipbetween a bearing area (%) and a bearing depth (nm) obtained bymeasuring the surface of the back surface conductive film with an atomicforce microscope be a predetermined relationship and a maximum height(Rmax) be in a predetermined range, to thereby reach this invention.Specifically, in order to solve the problem described above, thisinvention has the following structure.

This invention is a conductive film coated substrate having Structures 1to 3 described below, a multilayer reflective film coated substratehaving Structures 4 and 5, a reflective mask blank having Structure 6described below, a reflective mask having Structure 7 described below,and a semiconductor device manufacturing method having Structure 8described below.

(Structure 1)

According to Structure 1 of this invention, there is provided aconductive film coated substrate including a substrate for a mask blankfor use in lithography; and a conductive film formed on one main surfaceof the substrate, wherein, in a relationship between a bearing area (%)and a bearing depth (nm) that are obtained by measuring, with an atomicforce microscope, a region of 1 μm×1 μm of a surface of the conductivefilm, when a bearing area of 30% is defined as BA₃₀, a bearing area of70% is defined as BA₇₀, and bearing depths corresponding to the bearingareas of 30% and 70% are defined as BD₃₀ and BD₇₀, respectively, thesurface of the conductive film satisfies a relationship that(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) is 15 or more and 260 or less (%/nm), and amaximum height (Rmax) is 1.3 nm or more and 15 nm or less.

According to Structure 1, the relationship between the bearing area (%)and the bearing depth (nm) that are obtained by measuring, with anatomic force microscope, a region of 1 μm×1 μm of the surface of theconductive film is the predetermined relationship, and the maximumheight (Rmax) is in the predetermined range. Thus, when the conductivefilm coated substrate, and a multilayer reflective film coatedsubstrate, a reflective mask blank, and a reflective mask that aremanufactured using the same are inspected for a defect by a defectinspection apparatus, and, when coordinates of a fiducial mark formed onthe reflective mask blank and the multilayer reflective film coatedsubstrate and a transfer pattern of the reflective mask are measured bya coordinate measuring machine or the like, the positional accuracy of adefect detected by the defect inspection apparatus, the positionalaccuracy of the fiducial mark and the positional accuracy of thetransfer pattern determined by the coordinate measuring machine, and thelike may be improved. Specifically, according to Structure 1, when theconductive film coated substrate, and the multilayer reflective filmcoated substrate, the reflective mask blank, and the reflective maskthat are manufactured using the same are inspected and measured by adefect inspection apparatus, a coordinate measuring machine, and thelike, slippage of the back surface conductive film when the substrateand the like are fixed by the mount may be inhibited. Further, detectionof a pseudo defect due to surface roughness of the back surfaceconductive film may be inhibited to facilitate finding of a criticaldefect such as a foreign matter or a flaw.

(Structure 2)

According to Structure 2 of this invention, there is provided aconductive film coated substrate described in Structure 1, wherein, in afrequency distribution chart where a relationship between the bearingdepth obtained by measuring with the atomic force microscope and afrequency (%) of the obtained bearing depth of the surface of theconductive film is plotted, an absolute value of a bearing depthcorresponding to a center of a full width at half maximum, which isdetermined from an approximated curve drawn through the plotted pointsor a highest frequency of the plotted points, is smaller than anabsolute value of a bearing depth corresponding to ½ of the maximumheight (Rmax) of surface roughness of the surface of the conductivefilm.

According to Structure 2, in the frequency distribution chart in whichthe relationship between the predetermined bearing depth and thefrequency (%) of the predetermined bearing depth of the surface of theconductive film is plotted, the bearing depth has the predeterminedrelationship. Thus, unevenness forming the surface of the back surfaceconductive film has a surface geometry in which a ratio of depressedportions with respect to a reference level is larger than a ratio ofprojecting portions with respect to the reference level. Therefore,according to Structure 2, a problem of dust generation due to existenceof the projecting portions on the surface of the back surface conductivefilm may be prevented.

(Structure 3)

According to Structure 3 of this invention, there is provided aconductive film coated substrate described in Structure 1, wherein, in afrequency distribution chart where a relationship between the bearingdepth obtained by measuring with the atomic force microscope and afrequency (%) of the obtained bearing depth of the surface of theconductive film is plotted, an absolute value of a bearing depthcorresponding to a center of a full width at half maximum, which isdetermined from an approximated curve drawn through the plotted pointsor a highest frequency of the plotted points, is equal to or larger thanan absolute value of a bearing depth corresponding to ½ of the maximumheight (Rmax) of surface roughness of the surface of the conductivefilm.

According to Structure 3, in the frequency distribution chart in whichthe relationship between the predetermined bearing depth and thefrequency (%) of the predetermined bearing depth of the surface of theconductive film is plotted, the bearing depth has the predeterminedrelationship. Thus, unevenness forming the surface of the back surfaceconductive film has a surface geometry in which a ratio of projectingportions with respect to a reference level is larger than a ratio ofdepressed portions with respect to the reference level. Therefore,according to Structure 3, a foreign matter adhering to the back surfaceconductive film when a defect of a reflective mask blank and of amultilayer reflective film coated substrate is inspected and measured bya defect inspection apparatus, a coordinate measuring machine, and thelike, and when a back surface of a reflective mask is electrostaticallychucked and a semiconductor device is manufactured by an exposureapparatus may be effectively removed by a cleaning process.

(Structure 4)

According to Structure 4 of this invention, there is provided amultilayer reflective film coated substrate including a multilayerreflective film formed by alternately laminating a high refractive indexlayer and a low refractive index layer, wherein the multilayerreflective film is formed on a main surface of the conductive filmcoated substrate described in Structures 1 to 3 on a side opposite to aside on which the conductive film is formed.

According to Structure 4, EUV light at a predetermined wavelength may bereflected by the predetermined multilayer reflective film. Further, whenthe substrate provided with a multilayer reflective film according toStructure 3 is inspected and measured by a defect inspection apparatus,a coordinate measuring machine, and the like, slippage of the backsurface conductive film when the substrate and the like are fixed by themount may be inhibited.

(Structure 5)

According to Structure 5, there is provided a multilayer reflective filmcoated substrate described in Structure 4, further including aprotective film formed on the multilayer reflective film.

According to Structure 5, the protective film is formed on themultilayer reflective film. Thus, damage to a surface of the multilayerreflective film when the multilayer reflective film coated substrate isused to manufacture a reflective mask (EUV mask) may be inhibited.Therefore, reflectivity characteristics to EUV light becomesatisfactory.

(Structure 6)

According to Structure 6 of this invention, there is provided areflective mask blank including an absorber film formed on themultilayer reflective film or on the protective film of the multilayerreflective film coated substrate described in Structure 4 or 5.

According to Structure 6, the absorber film of the reflective mask blankmay absorb EUV light. Thus, a reflective mask (EUV mask) may bemanufactured by patterning the absorber film of the reflective maskblank. Further, according to Structure 6, when the reflective mask blankis inspected and measured by a defect inspection apparatus, a coordinatemeasuring machine, and the like, slippage of the back surface conductivefilm when the substrate and the like are fixed by the mount may beinhibited.

(Structure 7)

According to Structure 7, there is provided a reflective mask includingan absorber pattern provided on the multilayer reflective film, whereinthe absorber pattern is formed by patterning the absorber film of thereflective mask blank described in Structure 6.

According to the reflective mask of Structure 7, the multilayerreflective film has the absorber pattern formed thereon. Thus, apredetermined pattern may be transferred using EUV light to a transfertarget. Further, according to Structure 7, when the reflective mask isinspected and measured by a defect inspection apparatus, a coordinatemeasuring machine, and the like, slippage of the back surface conductivefilm when the substrate and the like are fixed by the mount may beinhibited.

(Structure 8)

According to Structure 8 of this invention, there is provided a methodof manufacturing a semiconductor device, including a step of performinga lithography process with the reflective mask described in Structure 7using an exposure apparatus to form a transfer pattern on a transfertarget.

According to the semiconductor device manufacturing method of Structure8, a semiconductor device having a fine and highly accurate transferpattern may be manufactured.

Effect of the Invention

According to the embodiments of this invention, the conductive filmcoated substrate, the multilayer reflective film coated substrate, thereflective mask blank, and the reflective mask may be provided, withwhich, when the reflective mask, the reflective mask blank, and themultilayer reflective film coated substrate are inspected for a defectby a defect inspection apparatus, and, when a fiducial mark formed onthe reflective mask blank and the multilayer reflective film coatedsubstrate and a transfer pattern of the reflective mask are measured bya coordinate measuring machine or the like, the positional accuracy of adefect detected by the defect inspection apparatus and the positionalaccuracy of the fiducial mark and a pattern such as the transfer patternby the coordinate measuring machine may be improved. Specifically,according to the embodiments of this invention, the reflective mask, thereflective mask blank, and the multilayer reflective film coatedsubstrate may be provided, which may, when the reflective mask, thereflective mask blank, and the multilayer reflective film coatedsubstrate are inspected/measured by a defect inspection apparatus, acoordinate measuring machine, and the like, inhibit slippage of the backsurface conductive film when the substrate and the like are fixed by amount. Further, according to the embodiments of this invention, thereflective mask blank and the multilayer reflective film coatedsubstrate may be provided, which may, at that time, inhibit detection ofa pseudo defect due to surface roughness of the back surface conductivefilm and facilitate finding of a critical defect such as a foreignmatter or a flaw.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1(a) shows a perspective view for illustrating a substrate for amask blank according to an embodiment of this invention. FIG. 1(b) showsa schematic sectional view for illustrating the substrate for a maskblank according to this embodiment.

FIG. 2 is a schematic sectional view for illustrating an exemplarystructure of a conductive film coated substrate according to anembodiment of this invention.

FIG. 3 is a schematic sectional view for illustrating an exemplarystructure of a multilayer reflective film coated substrate according toan embodiment of this invention.

FIG. 4 is a schematic sectional view for illustrating an exemplarystructure of a multilayer reflective film coated substrate according toan embodiment of this invention.

FIG. 5 is a schematic sectional view for illustrating an exemplarystructure of a reflective mask blank according to an embodiment of thisinvention.

FIG. 6 is a schematic sectional view for illustrating an exemplaryreflective mask according to an embodiment of this invention.

FIG. 7 is a schematic sectional view for illustrating another exemplarystructure of the reflective mask blank according to the embodiment ofthis invention.

FIG. 8 is a graph for showing results of bearing curve measurement ofsurface roughness of a back surface conductive film of a reflective maskblank of Examples 1 and 2 of this invention.

FIG. 9 is a graph for showing results of bearing curve measurement ofsurface roughness of a back surface conductive film of a reflective maskblank of Comparative Examples 1 and 2.

FIG. 10 is a schematic view of a mask for evaluating coordinatemeasurement having a fiducial mark and a pattern for evaluation.

FIG. 11 is a graph for showing a frequency distribution in which arelationship between a bearing depth (Depth) (nm) of Example 1 and afrequency (Hist.) (%) thereof is plotted.

MODES FOR EMBODYING THE INVENTION

This invention is a conductive film coated substrate in which theconductive film is formed on one surface of main surfaces of a substratefor a mask blank. A main surface of the main surfaces of the substratefor a mask blank on which the conductive film (also referred to as “backsurface conductive film”) is formed is referred to as a “back surface”.This invention is also a multilayer reflective film coated substrate inwhich a multilayer reflective film having a high refractive index layerand a low refractive index layer alternately laminated is formed on amain surface (sometimes simply referred to as “surface”) of theconductive film coated substrate having no conductive film formedthereon. This invention is also a reflective mask blank having amultilayer firm for a mask blank in which an absorber film is includedon a multilayer reflective film of a multilayer reflective film coatedsubstrate.

FIG. 2 is a schematic view for illustrating an exemplary substrate 50provided with a conductive film according to this invention. In thesubstrate 50 provided with a conductive film according to thisinvention, a back surface conductive film 23 is formed on a back surfaceof a substrate 10 for a mask blank. Note that, in this specification,the substrate 50 provided with a conductive film is a substrate in whichat least the back surface conductive film 23 is formed on the backsurface of the substrate 10 for a mask blank. A substrate in which amultilayer reflective film 21 is formed on another main surface(substrate 20 provided with a multilayer reflective film), a substratein which an absorber film 24 is further formed (reflective mask blank30), and the like are also included in the substrate 50 provided with aconductive film.

FIG. 7 is a schematic view for illustrating an exemplary reflective maskblank 30 according to this invention. The reflective mask blank 30according to this invention includes a multilayer firm 26 for a maskblank on a main surface of the substrate 10 for a mask blank. In thisspecification, the multilayer firm 26 for a mask blank is a plurality offilms including the multilayer reflective film 21 and the absorber film24 laminated and formed on the main surface of the substrate 10 for amask blank of the reflective mask blank 30. The multilayer firm 26 for amask blank can further include a protective film 22 formed between themultilayer reflective film 21 and the absorber film 24, and/or anetching mask film 25 formed on a surface of the absorber film 24. In thecase of the reflective mask blank 30 illustrated in FIG. 7, themultilayer firm 26 for a mask blank formed on the main surface of thesubstrate 10 for a mask blank has the multilayer reflective film 21, theprotective film 22, the absorber film 24, and the etching mask film 25.Note that, when the reflective mask blank 30 having the etching maskfilm 25 is used, as described later, the etching mask film 25 may beseparated after a transfer pattern is formed in the absorber film 24.Further, in the reflective mask blank 30 that does not have the etchingmask film 25 formed therein, the absorber film 24 may have a structurein which a plurality of layers are laminated and materials forming theplurality of layers may be materials having etching characteristicsdifferent from one another so that the reflective mask blank 30 mayinclude the absorber film 24 having the function of an etching mask.Further, a back surface of the reflective mask blank 30 of thisinvention includes the back surface conductive film 23. Therefore, thereflective mask blank 30 illustrated in FIG. 7 is a kind of thesubstrate 50 provided with a conductive film.

In this specification, “including a multilayer firm 26 for a mask blankon a main surface of the substrate 10 for a mask blank” includes, inaddition to a case in which the multilayer firm 26 for a mask blank isarranged in contact with the surface of the substrate 10 for a maskblank, a case in which another film is formed between the substrate 10for a mask blank and the multilayer firm 26 for a mask blank. The samecan be said for other films. Further, in this specification, forexample, “a film A is arranged in contact with a surface of a film B”means that the film A and the film B are arranged directly in contactwith each other without another film intervening between the film A andthe film B.

FIG. 5 is a schematic view for illustrating another exemplary reflectivemask blank 30 according to this invention. In the case of the reflectivemask blank 30 illustrated in FIG. 5, the multilayer firm 26 for a maskblank has the multilayer reflective film 21, the protective film 22, andthe absorber film 24, but does not have the etching mask film 25.Further, the reflective mask blank 30 illustrated in FIG. 5 includes theback surface conductive film 23 on the back surface thereof. Therefore,the reflective mask blank 30 illustrated in FIG. 5 is a kind of thesubstrate 50 provided with a conductive film.

FIG. 3 is an illustration of the substrate 20 provided with a multilayerreflective film. The multilayer reflective film 21 is formed on a mainsurface of the substrate 20 provided with a multilayer reflective filmillustrated in FIG. 3. FIG. 4 is an illustration of the substrate 20provided with a multilayer reflective film having the back surfaceconductive film 23 formed on a back surface thereof. The substrate 20provided with a multilayer reflective film illustrated in FIG. 4includes the back surface conductive film 23 on the back surfacethereof, and thus, is a kind of the substrate 50 provided with aconductive film.

The substrate 50 provided with a conductive film according to thisinvention has a feature in that a relationship between a bearing area(%) and a bearing depth (nm) that are obtained by measuring, with anatomic force microscope, a region of 1 μm×1 μm of a surface of the backsurface conductive film 23 is a predetermined relationship and a maximumheight (Rmax) of surface roughness is in a predetermined range.

According to the substrate 50 provided with a conductive film of thisinvention, when a defect of a reflective mask 40, the reflective maskblank 30, and the substrate 20 provided with a multilayer reflectivefilm are inspected and measured by a defect inspection apparatus, acoordinate measuring machine, and the like, the positional accuracy of adefect detected by the defect inspection apparatus and the positionalaccuracy of a fiducial mark or a pattern such as a transfer patterndetermined by the coordinate measuring machine can be improved. At thattime, detection of a pseudo defect due to surface roughness of the backsurface conductive film 23 can be inhibited to facilitate finding of acritical defect such as a foreign matter or a flaw.

Next, a relationship between the surface roughness (Rmax, Rms) as aparameter showing a surface geometry of the back surface conductive film23 and a bearing curve (bearing area (%) and bearing depth (nm)) isdescribed below.

First, root means square (Rms), which is a typical index of the surfaceroughness, is a root means square roughness, and is a square root of amean value of squares of deviations from an average line to ameasurement curve. Rms is represented by the following Expression (1):

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 1} \right\rbrack & \; \\{{Rms} = \sqrt{\frac{1}{l}{\int_{0}^{1}{{Z^{2}(x)}{\mathbb{d}x}}}}} & (1)\end{matrix}$

In Expression (1), l is a reference length and Z is a height from theaverage line to the measurement curve.

Rmax, which is a typical index of the surface roughness as well, is themaximum height of the surface roughness, and is an absolute differencebetween a maximum value of a height of a peak and a maximum value of adepth of a valley of a roughness curve.

Rms and Rmax are hitherto used for controlling a surface roughness ofthe substrate 10 for a mask blank, and are excellent in that the surfaceroughness can be numerically grasped. However, both of Rms and Rmax areinformation on height, and do not include information on minute changein surface geometry.

On the other hand, the bearing curve is formed by plotting ratios of anarea of a section of unevenness in a measurement region on the mainsurface of the substrate 10 that is cut by an arbitrary contour plane(level) to an area of the measurement region. The bearing curve enablesvisualization and conversion into a numerical form of variations of thesurface roughness of the back surface conductive film 23.

The bearing curve is generally plotted under a state in which thevertical axis represents the bearing area (%) and the horizontal axisrepresents the bearing depth (nm). A bearing area of 0 (%) represents ahighest point of a surface of a substrate measured, and a bearing areaof 100 (%) represents a lowest point of the surface of the substratemeasured. Therefore, a difference between the depth of the bearing areaof 0 (%) and the depth of the bearing area of 100 (%) is the maximumheight (Rmax) of the surface roughness described above. Note that,“bearing depth” as referred to in this invention is equivalent to“bearing height”. In the case of “bearing height”, opposite to the abovedescription, the bearing area of 0 (%) represents the lowest point ofthe surface of the substrate measured, and the bearing area of 100 (%)represents the highest point of the surface of the substrate measured.Control of the bearing curve in the back surface conductive film 23according to this embodiment is described below.

In the substrate 50 provided with a conductive film according to thisinvention, in the relationship between the bearing area (%) and thebearing depth (nm) that are obtained by measuring, with an atomic forcemicroscope, a region of 1 μm×1 μm of the surface of the back surfaceconductive film 23, when a bearing area of 30% is defined as BA₃₀, abearing area of 70% is defined as BA₇₀, and bearing depths correspondingto the bearing areas of 30% and 70% are defined as BD₃₀ and BD₇₀,respectively, the surface of the conductive film satisfies arelationship that (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) is 15 or more and 260 or less(%/nm) and the maximum height (Rmax) is 1.3 nm or more and 15 nm orless.

Specifically, (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) (unit: %/nm) described aboverepresents a slope of the bearing curve when the bearing area is from30% to 70%. By setting the slope to be 15 (%/nm) or more, the bearingarea reaches 100% with a smaller bearing depth (nm). In other words, theunevenness (surface roughness) of the surface of the reflective maskblank 30 maintains a very high level of smoothness and its surfacegeometry is uniform to a large extent. Thus, variations of theunevenness (surface roughness) as a cause of detecting a pseudo defectin defect inspection can be reduced, and thus, detection of a pseudodefect in defect inspection using a defect inspection apparatus can beinhibited, and further, a critical defect can be clarified.

Further, by setting the slope of the bearing curve to be 260 or less(%/nm), when the reflective mask 40, the reflective mask blank 30, andthe substrate 20 provided with a multilayer reflective film areinspected and measured by a defect inspection apparatus, a coordinatemeasuring machine, and the like, slippage of the back surface conductivefilm 23 when the substrate and the like are fixed by a mount can beinhibited. Therefore, when the reflective mask 40, the reflective maskblank 30, and the substrate 20 provided with a multilayer reflectivefilm are inspected for a defect by a defect inspection apparatus, and,when a fiducial mark formed on the reflective mask 40, the reflectivemask blank 30, and the substrate 20 provided with a multilayerreflective film and a transfer pattern of the reflective mask aremeasured by a coordinate measuring machine or the like, the positionalaccuracy of a defect detected by the defect inspection apparatus and thepositional accuracy of the fiducial mark or a pattern such as thetransfer pattern determined by the coordinate measuring machine can beimproved.

According to this invention, the region of 1 μm×1 μm may be in anarbitrary location in a region including, in manufacturing asemiconductor device using an exposure apparatus, a region in which theback surface of the reflective mask (back surface conductive film 23)abuts an electrostatic chuck and a region in which the back surface ofthe reflective mask (back surface conductive film 23) abuts the mount ofthe defect inspection apparatus or the coordinate measuring machine. Theabove-mentioned region including the region in which the electrostaticchuck abuts the back surface conductive film 23 and the region in whichthe mount of the defect inspection apparatus or the coordinate measuringmachine abuts can be, when the substrate 10 for a mask blank is in a6025 size (152 mm×152 mm×6.35 mm), for example, a region of 148 mm×148mm, a region of 146 mm×146 mm, a region of 142 mm×142 mm, or a region of132 mm×132 mm excluding a peripheral region on the surface of thereflective mask blank 30. Further, the arbitrary location can be, forexample, a region at the center of the back surface of the substrate 50provided with a conductive film on which the back surface conductivefilm 23 is formed and/or a region in which the mount of the defectinspection apparatus or the coordinate measuring machine abuts the backsurface conductive film 23 (abutting portion and a vicinity thereof).

Further, according to this invention, the region of 1 μm×1 μm can be aregion at the center of the back surface of the substrate 50 providedwith a conductive film on which the back surface conductive film 23 isformed and a region in which the defect inspection apparatus or thecoordinate measuring machine abuts the back surface conductive film 23.For example, when the film surface of the back surface conductive film23 is in a rectangular shape, the center is a point of intersection ofdiagonal lines of the rectangle. Specifically, the point of intersectionand the center of the region (the center of the region is the same asthe center of the surface of the back surface conductive film 23) arespatially coincident with each other.

From the viewpoint of inhibiting detection of a pseudo defect, it ispreferred that the surface of the back surface conductive film 23 of thesubstrate 50 provided with a conductive film have a surface geometry inwhich unevenness (surface roughness) forming the main surface isuniform. Therefore, (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) of the surface of the backsurface conductive film 23 is set to be 15 (%/nm) or more.(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) of the surface of the back surface conductivefilm 23 be preferably 20 (%/nm) or more, more preferably 30 (%/nm) ormore, still preferably 40 (%/nm) or more, and further preferably 50(%/nm) or more. From a similar viewpoint, the maximum height (Rmax) ofthe surface roughness of the surface of the back surface conductive film23 is set to be 15 nm or less. The maximum height (Rmax) of the surfaceroughness of the surface of the back surface conductive film 23 bepreferably 10 nm or less, more preferably 9 nm or less, and stillpreferably 8.5 nm or less.

Further, from the viewpoint of inhibiting slippage of the back surfaceconductive film 23 when the substrate and the like are fixed by themount, it is preferred that the surface of the back surface conductivefilm 23 of the substrate 50 provided with a conductive film have asurface geometry in which unevenness (surface roughness) forming themain surface is not completely uniform. Therefore,(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) of the surface of the back surface conductivefilm 23 is set to be 260 (%/nm) or less. (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) of thesurface of the back surface conductive film 23 be preferably 230 (%/nm)or less, and more preferably 200 (%/nm) or less. From a similarviewpoint, the maximum height (Rmax) of the surface roughness of thesurface of the back surface conductive film 23 be 1.3 nm or more,preferably 1.4 nm or more, and more preferably 1.5 nm or more.

From the above, with regard to the surface of the back surfaceconductive film 23 of the substrate 50 provided with a conductive film,preferably, in the relationship between the bearing area (%) and thebearing depth (nm) that are obtained by measuring, with an atomic forcemicroscope, a region of 1 μm×1 μm of the surface of the conductive film,when the bearing area of 30% is defined as BA₃₀, the bearing area of 70%is defined as BA₇₀, and the bearing depths corresponding to the bearingareas of 30% and 70% are defined as BD₃₀ and BD₇₀, respectively, thesurface of the conductive film satisfies the relationship that(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) is 15 or more and 260 or less (%/nm), preferably20 or more and 260 or less (%/nm), and the maximum height (Rmax) is 1.3nm or more and 15 nm or less, preferably 1.3 nm or more and 10 nm orless.

Further, the surface roughness of the surface of the back surfaceconductive film 23 can be controlled through, in addition to the maximumheight (Rmax) described above, the root means square roughness (Rms). Itis preferred that the root means square roughness (Rms) obtained bymeasuring, with an atomic force microscope, a region of 1 μm×1 μm of thesurface of the back surface conductive film 23 be 0.15 nm or more and1.0 nm or less.

Further, it is preferred that the surface of the back surface conductivefilm 23 have a surface geometry in which, in a frequency distributionchart where the relationship between the bearing depth obtained bymeasurement with an atomic force microscope and the frequency (%) of theobtained bearing depth is plotted, an absolute value of the bearingdepth corresponding to a center of a full width at half maximumdetermined from an approximated curve drawn through the plotted pointsor a highest frequency of the plotted points is smaller than an absolutevalue of the bearing depth corresponding to ½ (half) of the maximumheight (Rmax) of the surface roughness of the surface of the backsurface conductive film 23. Unevenness forming the surface of the backsurface conductive film 23 is a surface geometry in which a ratio ofdepressed portions with respect to a reference level is larger than aratio of projecting portions with respect to the reference level.Therefore, a problem of dust generation due to existence of theprojecting portions on the surface of the back surface conductive film23 can be prevented.

Further, from the viewpoint of more effectively removing a foreignmatter adhering to the back surface conductive film by a cleaningprocess, it is preferred that the surface of the back surface conductivefilm 23 have a surface geometry in which, in a frequency distributionchart where the relationship between the bearing depth obtained bymeasurement with an atomic force microscope and the frequency (%) of theobtained bearing depth is plotted, the absolute value of the bearingdepth corresponding to the center of the full width at half maximumdetermined from the approximated curve drawn through the plotted pointsor the highest frequency of the plotted points is equal to or largerthan the absolute value of the bearing depth corresponding to ½ (half)of the maximum height (Rmax) of the surface roughness of the surface ofthe back surface conductive film 23. Unevenness forming the surface ofthe back surface conductive film 23 is a surface geometry in which theratio of the projecting portions with respect to the reference level islarger than the ratio of the depressed portions with respect to thereference level. Therefore, an effect can be obtained that when a defectof the reflective mask blank and of the multilayer reflective filmcoated substrate is inspected and measured by a defect inspectionapparatus, a coordinate measuring machine, and the like, and when theback surface of the reflective mask is electrostatically chucked and asemiconductor device is manufactured by an exposure apparatus, a foreignmatter adhering to the back surface conductive film can be effectivelyremoved by the cleaning process.

Next, a power spectrum density (PSD) representing the surface geometryof the surface of the back surface conductive film 23 is describedbelow.

As described above, Rms and Rmax are hitherto used for controlling thesurface roughness of the substrate 10 for a mask blank, and areexcellent in that the surface roughness can be numerically grasped.However, both of Rms and Rmax are information on height, and do notinclude information on minute change in surface shape.

On the other hand, power spectrum analysis that represents the obtainedunevenness of the surface as amplitude intensity in spatial frequency bytransformation into a spatial frequency region can convert minutesurface shape into a numerical form. When data of height in an xcoordinate and a y coordinate is represented by Z(x, y), Fouriertransform thereof is given by Expression (2) below:

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 2} \right\rbrack & \; \\{{F\left( {u,v} \right)} = {\frac{1}{N_{x}N_{y}}{\sum\limits_{u = 0}^{N_{x} - 1}{\sum\limits_{v = 0}^{N_{y} - 1}{{Z\left( {x,y} \right)}{\exp\left\lbrack {{- {\mathbb{i}}}\; 2\;{\pi\left( {\frac{ux}{N_{x}} + \frac{vy}{N_{y}}} \right)}} \right\rbrack}}}}}} & (2)\end{matrix}$

Here, Nx and Ny are the numbers of data in an x direction and a ydirection, respectively. u=0, 1, 2 . . . Nx−1 and v=0, 1, 2 . . . Ny−1are established. A spatial frequency f at this time is given byExpression (3) below:

$\begin{matrix}\left\lbrack {{Math}.\mspace{14mu} 3} \right\rbrack & \; \\{f = \left\{ {\left\lbrack \frac{u}{\left( {N_{x} - 1} \right)d_{x}} \right\rbrack^{2} + \left\lbrack \frac{v}{\left( {N_{y} - 1} \right)d_{y}} \right\rbrack^{2}} \right\}^{1/2}} & (3)\end{matrix}$

Here, in Expression (3), dx is a minimum resolution in the x directionand dy is a minimum resolution in the y direction.

The power spectrum density PSD at this time is given by Expression (4)below:

[Math. 4]P(u,v)=|F(u,v)|²  (4)

This power spectrum analysis is excellent in that change in surfacegeometry of the back surface conductive film 23 can be grasped not onlyas simple change in height but also as change thereof in the spatialfrequency, and is a method of analyzing how a microscopic reaction on anatomic level and the like affects the surface.

In the substrate 50 provided with a conductive film according to thisinvention, in order to attain the objects described above, it ispreferred that the surface of the back surface conductive film 23 have apower spectrum density of 30 nm⁴ or more and 200 nm⁴ or less in aspatial frequency of 1 μm⁻¹ or more and 100 μm⁻¹ or less obtained bymeasuring a region of 1 μm×1 μm with an atomic force microscope.

The region of 1 μm×1 μm may be in a location in a region including, inmanufacturing a semiconductor device using an exposure apparatus, aregion in which the back surface of the reflective mask (back surfaceconductive film 23) abuts an electrostatic chuck and a region in whichthe back surface of the reflective mask (back surface conductive film23) abuts the mount of the defect inspection apparatus or the coordinatemeasuring machine. The above-mentioned region including the region inwhich the electrostatic chuck abuts the back surface conductive film 23and the region in which the mount of the defect inspection apparatus orthe coordinate measuring machine abuts can be, when the substrate 10 fora mask blank is in a 6025 size (152 mm×152 mm×6.35 mm), for example, aregion of 148 mm×148 mm, a region of 146 mm×146 mm, a region of 142mm×142 mm, or a region of 132 mm×132 mm excluding a peripheral region onthe surface of the reflective mask blank 30. Further, theabove-mentioned arbitrary location may be, for example, a region at thecenter of the back surface of the substrate 50 provided with aconductive film on which the back surface conductive film 23 is formedand/or a region in which the mount of the defect inspection apparatus orthe coordinate measuring machine abuts the back surface conductive film23 (abutting portion and a vicinity thereof).

Further, according to this invention, the region of 1 μm×1 μm can be aregion at the center of the surface of the back surface conductive film23 of the substrate 50 provided with a conductive film and/or a regionin which the defect inspection apparatus or the coordinate measuringmachine abuts the back surface conductive film 23. For example, when thesurface of the back surface conductive film 23 of the substrate 50provided with a conductive film is in a rectangular shape, the center isa point of intersection of diagonal lines of the rectangle.Specifically, the point of intersection and the center of the region(the center of the region is the same as the center of the surface ofthe film) are spatially coincident with each other.

Next, the substrate 50 provided with a conductive film according to thisinvention is specifically described.

[Substrate 10 for Mask Blank]

First, the substrate 10 for a mask blank that can be used inmanufacturing the back surface conductive film 23 according to thisinvention is described below.

FIG. 1(a) is a perspective view for illustrating an exemplary substrate10 for a mask blank that can be used in manufacturing the back surfaceconductive film 23 according to this invention. FIG. 1(b) is a schematicsectional view of the substrate 10 for a mask blank illustrated in FIG.1(a).

The substrate 10 for a mask blank (or, sometimes simply referred to assubstrate 10) is a plate-like body in a rectangular shape, and has twoopposed main surfaces 2 and end faces 1. The two opposed main surfaces 2are an upper surface and a lower surface of the plate-like body, and areformed so as to be opposed to each other. Further, at least one of thetwo opposed main surfaces 2 is the main surface on which the transferpattern is to be formed.

An end face 1 is a side surface of the plate-like body, and is adjacentto edges of the opposed main surfaces 2. The end face 1 has a planar endface portion 1 d and a curved end face portion 1 f. The planar end faceportion 1 d is a surface that connects a side of one opposed mainsurface 2 and a side of another opposed main surface 2, and includes aside surface portion 1 a and beveled portions 1 b. The side surfaceportion 1 a is a portion approximately perpendicular to the opposed mainsurfaces 2 of the planar end face portion 1 d (T plane). The beveledportion 1 b is a beveled portion between the side surface portion 1 aand the opposed main surface 2 (C plane), and is formed between the sidesurface portion 1 a and the opposed main surface 2.

The curved end face portion if is a portion adjacent to a vicinity of acorner portion 10 a of the substrate 10 when the substrate 10 is seen inplan view (R portion), and includes a side surface portion 1 c andbeveled portions 1 e. Here, to see the substrate 10 in plan view is tosee the substrate 10 from, for example, a direction perpendicular to theopposed main surfaces 2. Further, the corner portion 10 a of thesubstrate 10 is, for example, a vicinity of an intersection of two sidesat edges of the opposed main surfaces 2. An intersection of two sidesmay be an intersection of extensions of the two sides. In this example,the curved end face portion if is formed so as to be curved by roundingthe corner portion 10 a of the substrate 10.

Further, it is preferred that the main surfaces of the substrate 10 fora mask blank be surfaces to which surface treatment is applied bycatalyst-referred etching. Catalyst-referred etching (hereinafter alsoreferred to as CARE) is a surface treatment method in which an object tobe treated (substrate 10 for a mask blank) and a catalyst are placed ina treatment liquid or the treatment liquid is supplied between theobject to be treated and the catalyst, the object to be treated and thecatalyst are brought into contact with each other, and the object to betreated is treated by an active species generated from a molecule in thetreatment liquid adsorbed on the catalyst at that time. Note that, whenthe object to be treated is formed of a solid oxide such as glass, thetreatment liquid is water, the object to be treated and the catalyst arebrought into contact with each other in the presence of water, and thecatalyst and a surface of the object to be treated are relatively movedor the like, thereby removing a product of hydrolytic degradation fromthe surface of the object to be treated to apply the treatment.

Surface treatment is selectively applied to the main surfaces of thesubstrate 10 for a mask blank by catalyst-referred etching from theprojecting portions in contact with a surface of the catalyst as thereference level. Therefore, the unevenness (surface roughness) formingthe main surfaces maintains a very high level of smoothness and itssurface geometry is uniform to a large extent. In addition, in thesurface geometry, the ratio of the depressed portions with respect tothe reference level is larger than the ratio of the projecting portionswith respect to the reference level. Therefore, when a plurality of thinfilms are laminated on the main surface, a defect size on the mainsurface tends to be small, and thus, from the viewpoint of defectquality, surface treatment by catalyst-referred etching is preferred. Inparticular, the effect is especially exerted when the multilayerreflective film 21 and the back surface conductive film 23 describedbelow are formed on the main surface.

Note that, when a material of the substrate 10 is a glass material, asthe catalyst, at least one material selected from the group consistingof platinum, gold, transition metals, and alloys including at least onethereof can be used. Further, as the treatment liquid, at least onetreatment liquid selected from the group consisting of functional waterssuch as pure water, ozone water, and hydrogen water, a low-concentrationalkaline aqueous solution, and a low-concentration acidic aqueoussolution can be used.

It is preferred that, in the substrate 10 for a mask blank used for theback surface conductive film 23 according to this invention, the mainsurface on the side on which the transfer pattern is to be formed besurface treated so as to be highly flat from the viewpoint of obtainingat least pattern transfer accuracy and positional accuracy. In the caseof the substrate 10 for an EUV reflective mask blank, in a region of 132mm×132 mm or in a region of 142 mm×142 mm of the main surface of thesubstrate 10 on the side on which the transfer pattern is to be formed,the flatness is preferably 0.1 μm or less, and particularly preferably0.05 μm or less. More preferably, in a region of 132 mm×132 mm of themain surface of the substrate 10 on the side on which the transferpattern is to be formed, the flatness is 0.03 μm or less. Further, themain surface on the side opposite to the side on which the transferpattern is to be formed is the surface that is electrostatically chuckedwhen setting on an exposure apparatus is carried out, and, in a regionof 142 mm×142 mm thereof, the flatness is 1 μm or less, and,particularly preferably, 0.5 μm or less.

A material of the substrate 10 for a reflective mask blank for EUVexposure may be anything having low thermal expansion characteristics.For example, so-called multicomponent-based glass having low thermalexpansion characteristics such as SiO₂—TiO₂-based glass (binary(SiO₂—TiO₂) and ternary (such as SiO₂—TiO₂—SnO₂)), for example,SiO₂—Al₂O₃—Li₂O-based crystallized glass, can be used. Further, thesubstrate 10 formed of, other than the glasses described above, silicon,a metal, or the like can also be used. An Invar alloy (Fe—Ni basedalloy) is an example of the metal substrate 10.

As described above, in the case of the substrate 10 for a mask blank forEUV exposure, the substrate 10 is required to have low thermal expansioncharacteristics, and thus, a multicomponent-based glass material is usedtherefor. However, there is a problem that a multicomponent-based glassmaterial is less liable to attain a high level of smoothness comparedwith synthetic quartz glass. In a quest to solve this problem, a thinfilm formed of a metal or an alloy, or a material containing any one ofthese and at least one of oxygen, nitrogen, and carbon is formed on thesubstrate 10 formed of a multicomponent-based glass material. By mirrorpolishing and surface treating a surface of such a thin film, a desiredsurface can be formed relatively easily.

In particular, the following material is preferred as the material forthe thin film: tantalum (Ta), an alloy containing Ta, or a Ta compoundcontaining any one of Ta and the alloy containing Ta as well as at leastone of oxygen, nitrogen, and carbon. For example, the following materialmay be applied as the Ta compound: TaB, TaN, TaO, TaON, TaCON, TaBN,TaBO, TaBON, TaBCON, TaHf, TaHfO, TaHfN, TaHfON, TaHfCON, TaSi, TaSiO,TaSiN, TaSiON, or TaSiCON. Of those Ta compounds, the following nitrogen(N)-containing compound is more preferred: TaN, TaON, TaCON, TaBN,TaBON, TaBCON, TaHfN, TaHfON, TaHfCON, TaSiN, TaSiON, or TaSiCON. Notethat, from the viewpoint of high smoothness of the surface of the thinfilm, the thin film preferably have an amorphous structure. A crystalstructure of the thin film can be measured by an X-ray diffractometer(XRD).

[Substrate 20 Provided with Multilayer Reflective Film]

Next, the substrate 20 provided with a multilayer reflective film thatcan be used for the back surface conductive film 23 and the reflectivemask blank 30 according to this invention is described below.

FIG. 3 is a schematic view for illustrating an exemplary substrate 20provided with a multilayer reflective film that can be used for the backsurface conductive film 23 and the reflective mask blank 30 according tothis invention. FIG. 4 is a schematic view for illustrating anotherexemplary substrate 20 provided with a multilayer reflective filmaccording to this invention. As illustrated in FIG. 4, when thesubstrate 20 provided with a multilayer reflective film has thepredetermined back surface conductive film 23, the substrate 20 providedwith a multilayer reflective film is a kind of the back surfaceconductive film 23 according to this invention. In this specification,both of the substrates 20 provided with a multilayer reflective filmillustrated in FIG. 3 and FIG. 4 are referred to as the substrate 20provided with a multilayer reflective film according to this embodiment.

The substrate 20 provided with a multilayer reflective film according tothis embodiment has a structure in which the multilayer reflective film21 is formed on the main surface of the substrate 10 for a mask blankdescribed above on the side on which the transfer pattern is to beformed. The multilayer reflective film 21 gives the function ofreflecting EUV light to the reflective mask 40 for EUV lithography, andthe multilayer reflective film 21 has a structure in which elementshaving different refractive indices are periodically laminated.

A material of the multilayer reflective film 21 is not specificallylimited insofar as EUV light is reflected, but the material alonegenerally has a reflectivity of 65% or more, and an upper limit thereofis generally 73%. Such a multilayer reflective film 21 can typically bethe multilayer reflective film 21 in which a thin film formed of amaterial having a high refractive index (high refractive index layer)and a thin film formed of a material having a low refractive index (lowrefractive index layer) are alternately laminated for about 40 cycles toabout 60 cycles.

For example, it is preferred that the multilayer reflective film 21 forEUV light having a wavelength of from 13 nm to 14 nm be an Mo/Siperiodic multilayer firm in which an Mo film and a Si film arealternately laminated for about 40 cycles. Other than this, as themultilayer reflective film 21 used in a region of EUV light, a Ru/Siperiodic multilayer firm, an Mo/Be periodic multilayer firm, an Mocompound/Si compound periodic multilayer firm, a Si/Nb periodicmultilayer firm, a Si/Mo/Ru periodic multilayer firm, a Si/Mo/Ru/Moperiodic multilayer firm, a Si/Ru/Mo/Ru periodic multilayer firm, or thelike can be used.

A method of forming the multilayer reflective film 21 is publicly knownin the art, and the formation can be carried out by forming the layersby, for example, magnetron sputtering or ion beam sputtering. In thecase of the Mo/Si periodic multilayer firm described above, for example,by ion beam sputtering, first, a Si film having a thickness of aboutseveral nanometers is formed on the substrate 10 using a Si target, andafter that, an Mo film having a thickness of about several nanometers isformed using an Mo target, and the cycle is repeated for 40 cycles to 60cycles to laminate the layers and to form the multilayer reflective film21.

When the substrate 20 provided with a multilayer reflective filmaccording to this embodiment is manufactured, it is preferred that themultilayer reflective film 21 be formed by ion beam sputtering in whichan ion beam is alternately radiated to a sputtering target of a materialhaving a high refractive index and a sputtering target of a materialhaving a low refractive index. By forming the multilayer reflective film21 by the predetermined ion beam sputtering, the multilayer reflectivefilm 21 having satisfactory reflectivity characteristics for EUV lightcan be obtained with reliability.

With regard to the substrate 20 provided with a multilayer reflectivefilm according to this embodiment, it is preferred that the multilayerfirm 26 for a mask blank further include the protective film 22 arrangedso as to be in contact with a surface of the multilayer reflective film21 on a side opposite to the substrate 10 for a mask blank.

The protective film 22 (see FIG. 5) can be formed on the multilayerreflective film 21 formed as described above for the purpose ofprotecting the multilayer reflective film 21 from dry etching and wetcleaning in a manufacturing process of the reflective mask 40 for EUVlithography. An embodiment in which the multilayer reflective film 21and the protective film 22 are formed on the substrate 10 for a maskblank as described above can also be the substrate 20 provided with amultilayer reflective film according to this embodiment.

Note that, a material such as Ru, Ru—(Nb, Zr, Y, B, Ti, La, Mo), Si—(Ru,Rh, Cr, B), Si, Zr, Nb, La, or B may be used as a material for theprotective film 22. Of those, the application of a ruthenium(Ru)-containing material results in better reflectivity characteristicsof the multilayer reflective film 21. Specifically, the material ispreferably Ru or Ru—(Nb, Zr, Y, B, Ti, La, Mo). The protective film 22is particularly effective when the absorber film 24 is of a Ta-basedmaterial and the absorber film 24 is patterned by dry etching with aCl-based gas.

For the purpose of forming the multilayer reflective film 21 or theprotective film 22 to have a satisfactory geometry, it is preferredthat, in forming the multilayer reflective film 21, the high refractiveindex layer and the low refractive index layer be formed by sputteringso as to be deposited diagonally with respect to a normal to the mainsurface of the substrate 10. More specifically, it is good that, in thefilm formation, an incident angle of sputtering particles for forming alow refractive index layer of Mo or the like and an incident angle ofsputtering particles for forming a high refractive index layer of Si orthe like be more than 0 degrees and 45 degrees or less. The angles aremore preferably more than 0 degrees and 40 degrees or less, and furtherpreferably more than 0 degrees and 30 degrees or less. Further, it ispreferred that the protective film 22 formed on the multilayerreflective film 21 be formed by ion beam sputtering so that theprotective film 22 is also deposited diagonally with respect to thenormal to the main surface of the substrate 10 successively after themultilayer reflective film 21 is formed.

[Substrate 50 Provided with Conductive Film]

Next, the substrate 50 provided with a conductive film according to thisinvention is described. In the substrate 20 provided with a multilayerreflective film illustrated in FIG. 3, by forming the predetermined backsurface conductive film 23 on the surface of the substrate 10 on theside opposite to the surface in contact with the multilayer reflectivefilm 21, the substrate 50 provided with a conductive film according tothis invention (substrate 20 provided with a multilayer reflective filmaccording to this invention) as illustrated in FIG. 4 can be obtained.Note that, as illustrated in FIG. 2, by forming the predetermined backsurface conductive film 23 on one surface of the main surfaces of thesubstrate 10 for a mask blank, the substrate 50 provided with aconductive film according to this invention can be obtained.

An electrical characteristic (sheet resistance) required of the backsurface conductive film 23 is ordinarily 100 Ω/□ or less. A method offorming the back surface conductive film 23 is publicly known, and theformation can be performed by, for example, magnetron sputtering or ionbeam sputtering using a target of a metal such as Cr or Ta or an alloythereof.

It is preferred that the back surface conductive film 23 be formed bysputtering using a sputtering target that contains a metal as a materialof the conductive film. Specifically, it is preferred that the backsurface conductive film 23 be formed by, under a state in which thesurface of the substrate 10 on which the back surface conductive film 23is to be formed faces upward and the substrate 10 is rotated on ahorizontal plane, sputtering a sputtering target opposed to the surfaceon which the film is to be formed so as to be slanted at a predeterminedangle, at a position at which a central axis of the substrate 10 and astraight line that passes through a center of the sputtering target andthat is in parallel with the central axis of the substrate 10 are notspatially coherent. It is preferred that the predetermined angle of theslanted sputtering target be 5 degrees or more and 30 degrees or less.Further, it is preferred that a gas pressure in the film formation bysputtering be 0.05 Pa or more and 0.5 Pa or less. By forming the backsurface conductive film 23 by such a method, in the substrate 50provided with a conductive film, the relationship between the bearingarea (%) and the bearing depth (nm) that are obtained by measuring, withan atomic force microscope, a region of 1 μm×1 μm of the surface of theback surface conductive film 23 can be the predetermined relationship,and the maximum height (Rmax) of the surface roughness can be in thepredetermined range.

Further, in the substrate 50 provided with a conductive film accordingto this invention, an underlayer may be formed between the substrate 10and the multilayer reflective film 21. The underlayer can be formed forthe purpose of improving the smoothness of the main surface of thesubstrate 10, for the purpose of reducing defects, for the purpose of aneffect of enhancing the reflectivity of the multilayer reflective film21, and for the purpose of correcting stress on the multilayerreflective film 21.

[Reflective Mask Blank 30]

Next, the reflective mask blank 30 according to this invention isdescribed. FIG. 5 is a schematic view for illustrating an exemplaryreflective mask blank 30 according to this invention. The reflectivemask blank 30 according to this invention has a structure in which theabsorber film 24 to be the transfer pattern is formed on the multilayerreflective film 21 or on the protective film 22 of the substrate 20provided with a multilayer reflective film described above.

The absorber film 24 has the function of absorbing EUV light as exposurelight, and it is enough that, in the reflective mask 40 manufacturedusing the reflective mask blank 30, there is a desired reflectivitydifference between light reflected by the multilayer reflective film 21or the protective film 22 and light reflected by an absorber pattern 27.

For example, the absorber film 24 is set to have a reflectivity of 0.1%or more and 40% or less for EUV light. Further, there may be, inaddition to the reflectivity difference described above, a desired phasedifference between light reflected by the multilayer reflective film 21or the protective film 22 and light reflected by the absorber pattern27. Note that, when there is the desired phase difference between suchreflected lights, there is a case in which the absorber film 24 in thereflective mask blank 30 is referred to as a phase shift film.

When the desired phase difference is provided between the reflectedlights to improve contrast of light obtained by being reflected by thereflective mask 40, it is preferred that the phase difference be set ina range of 180 degrees±10 degrees, the absorber film 24 be set to havean absolute reflectivity of 1.5% or more and 30% or less, and theabsorber film 24 have a reflectivity of 2% or more and 40% or less withrespect to the surface of the multilayer reflective film 21 and/or theprotective film 22.

The absorber film 24 may be a single layer or may have a laminatedstructure. In the case of the laminated structure, the absorber film 24may be any one of a laminated film of the same material and a laminatedfilm of different materials. The material or composition of thelaminated film may be changed in stages and/or continuously in athickness direction.

A material of the absorber film 24 is not specifically limited. Forexample, it is preferred that a material having the function ofabsorbing EUV light, and formed solely of Ta (tantalum) or containing Taas a main component thereof be used. The material that contains Ta as amain component thereof is ordinarily an alloy of Ta. It is preferredthat, from the viewpoint of smoothness and flatness, a crystal state ofthe absorber film 24 be amorphous or microcrystalline. As the materialthat contains Ta as a main component thereof, for example, a materialcontaining Ta and B, a material containing Ta and N, a materialcontaining Ta and B, and further containing at least any one of O and N,a material containing Ta and Si, a material containing Ta, Si, and N, amaterial containing Ta and Ge, a material containing Ta, Ge, and N, orthe like can be used. Further, for example, by adding B, Si, Ge, or thelike to Ta, an amorphous structure can be easily obtained to improve thesmoothness. Further, by further adding N or O to Ta, resistance tooxidation can be improved to improve stability over time. It ispreferred that the absorber film 24 have a microcrystalline structure oran amorphous structure. The crystal structure can be confirmed using anX-ray diffractometer (XRD).

Specific examples of the tantalum-containing material for forming theabsorber film 24 include a tantalum metal and a material containingtantalum as well as one or more elements selected from nitrogen, oxygen,boron and carbon and being substantially free of hydrogen. Examplesthereof include Ta, TaN, TaON, TaBN, TaBON, TaCN, TaCON, TaBCN, andTaBOCN. The material described above may contain a metal other thantantalum insofar as the effect of this invention can be obtained. Whenthe material containing tantalum that forms the absorber film 24contains boron, it is easy to control the absorber film 24 so as to havean amorphous structure (non-crystalline).

It is preferred that the absorber film 24 of the reflective mask blankaccording to this invention be formed of a material containing tantalumand nitrogen. A nitrogen content in the absorber film 24 is preferably30 at % or less, more preferably 25 at % or less, and further preferably20 at % or less. It is preferred that the nitrogen content in theabsorber film 24 be 5 at % or more.

In the reflective mask blank 30 according to this invention, it ispreferred that the absorber film 24 contain tantalum and nitrogen, andthe nitrogen content therein be 10 at % or more and 50 at % or less. Theabsorber film 24 contains tantalum and nitrogen, and the nitrogencontent is 10 at % or more and 50 at % or less, and thus, on a surfaceof the absorber film 24, the predetermined relationship between thebearing area (%) and the bearing depth (nm) and the predetermined rangeof the maximum height (Rmax) that are described above can be obtained.Further, increase in size of crystal particles that form the absorberfilm 24 can be inhibited, and thus, pattern edge roughness when theabsorber film 24 is patterned can be reduced.

In the reflective mask blank 30 according to this invention, thethickness of the absorber film 24 is set to be a thickness that isnecessary for the difference between light reflected by the multilayerreflective film 21 or the protective film 22 and light reflected by theabsorber pattern 27 is the desired reflectivity difference. It ispreferred that the thickness of the absorber film 24 be 60 nm or lessfor the purpose of reducing a shadowing effect.

Further, in the reflective mask blank 30 according to this invention,the absorber film 24 can have a phase shift function of having thedesired phase difference between light reflected by the multilayerreflective film 21 or the protective film 22 and light reflected by theabsorber pattern 27. In that case, the reflective mask blank 30 as amaster for the reflective mask 40 with improved transfer resolution byEUV light is obtained. Further, the thickness of the absorber film 24necessary for exerting a phase shift effect necessary for obtaining thedesired transfer resolution can be thinner than a related-art one, andthus, a reflective mask blank with a reduced shadowing effect isobtained.

A material of the absorber film 24 having the phase shift function isnot particularly limited. For example, sole Ta or a material thatcontains Ta as a main component thereof described above may be used, andother materials may also be used. Examples of the materials other thanTa include Ti, Cr, Nb, Mo, Ru, Rh, and W. In addition, examples thereofmay include: an alloy containing two or more elements of Ta, Ti, Cr, Nb,Mo, Ru, Rh, and W; and a laminate film of those elements. In addition,these materials may each contain one or more elements selected fromnitrogen, oxygen, and carbon.

Note that, when the absorber film 24 is a laminated film, the absorberfilm 24 may be a laminated film of layers of the same material or alaminated film of layers of different materials. When the absorber film24 is a laminated film of layers of different materials, materialsforming the plurality of layers may have etching characteristicsdifferent from one another so that the absorber film 24 has the functionof an etching mask.

Note that, the reflective mask blank 30 according to this invention isnot limited to the structure illustrated in FIG. 5. For example, aresist film to be a mask for patterning the absorber film 24 may beformed on the absorber film 24, and the reflective mask blank 30provided with the resist film can also be the reflective mask blank 30according to this invention. Note that, the resist film formed on theabsorber film 24 may be a positive type or a negative type. Further, theresist film may be for drawing with an electron beam or may be fordrawing with a laser. Further, a so-called hard mask film (etching maskfilm 25) may be formed between the absorber film 24 and the resist film,and this embodiment can also be the reflective mask blank 30 accordingto this invention.

It is preferred that, in the reflective mask blank 30 according to thisinvention, the multilayer firm 26 for a mask blank further include theetching mask film 25 arranged so as to be in contact with a surface ofthe absorber film 24 on a side opposite to the substrate 10 for a maskblank. In the case of the reflective mask blank 30 illustrated in FIG.7, the multilayer firm 26 for a mask blank on the main surface of thesubstrate 10 for a mask blank further has the etching mask film 25 inaddition to the multilayer reflective film 21, the protective film 22,and the absorber film 24. The reflective mask blank 30 according to thisinvention can further have a resist film on an outermost surface of themultilayer firm 26 for a mask blank of the reflective mask blank 30illustrated in FIG. 7.

Specifically, the reflective mask blank 30 according to this inventionhas a structure in which, when sole Ta or a material that contains Ta asa main component thereof is used as the material of the absorber film24, the etching mask film 25 formed of a material containing chromium isformed on the absorber film 24. When the reflective mask blank 30 hassuch a structure, even if, after the transfer pattern is formed in theabsorber film 24, the etching mask film 25 is separated by dry etchingusing a gas mixture of a chlorine-based gas and oxygen gas, thereflective mask 40 in which optical characteristics of the absorberpattern 27 are satisfactory can be manufactured. Further, the reflectivemask 40 in which line edge roughness of the transfer pattern formed inthe absorber film 24 is satisfactory can be manufactured.

An example of the chromium-containing material for forming the etchingmask film 25 is a material containing chromium as well as one or moreelements selected from nitrogen, oxygen, carbon, and boron. Examplesthereof include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN.The material described above may contain a metal other than chromiuminsofar as the effect of this invention can be obtained. From theviewpoint of obtaining the function as an etching mask for accuratelyforming the transfer pattern in the absorber film 24, it is desired thatthe etching mask film 25 have a thickness of 3 nm or more. Further, fromthe viewpoint of reducing the thickness of the resist film, it isdesired that the etching mask film 25 have a thickness of 15 nm or less.

Next, a method of manufacturing the reflective mask blank 30 accordingto this invention is described under a state in which the substrate 20provided with a multilayer reflective film illustrated in FIG. 4 is astarting material. In the method of manufacturing the reflective maskblank 30 according to this invention, the absorber film 24 is formed onthe multilayer reflective film 21 that is formed on the main surface ofthe substrate 10 for a mask blank. Note that, when the substrate 20provided with a multilayer reflective film illustrated in FIG. 2 isused, the predetermined back surface conductive film 23 is furtherformed on the back surface of the substrate 10 as described above.

In a step of forming the absorber film 24 in the method of manufacturingthe reflective mask blank 30 according to this invention, it ispreferred that the absorber film 24 be formed by reactive sputteringusing a sputtering target formed of a material contained in the absorberfilm 24, and the absorber film 24 be formed so as to contain a componentcontained in an atmospheric gas in the reactive sputtering. In the filmformation by reactive sputtering, through adjustment of the flow rate ofthe atmospheric gas, adjustment can be made so that the surface shape isa predetermined shape.

When the absorber film 24 is formed by reactive sputtering, it ispreferred that the atmospheric gas be a gas mixture including an inertgas and nitrogen gas. In this case, the flow rate of nitrogen can beadjusted, and thus, the absorber film 24 having appropriate compositioncan be obtained.

In the method of manufacturing the reflective mask blank 30 according tothis invention, it is preferred that the absorber film 24 be formedusing a sputtering target of a material containing tantalum. As aresult, the absorber film 24 that contains tantalum and thatappropriately absorbs light can be formed.

It is preferred that the method of manufacturing the reflective maskblank 30 according to this invention further include a step of formingthe protective film 22 arranged so as to be in contact with the surfaceof the multilayer reflective film 21. By forming the protective film 22,damage to the surface of the multilayer reflective film 21 when thereflective mask (EUV mask) is manufactured can be inhibited, and thus,the reflectivity characteristics for EUV light becomes moresatisfactory. Further, in the reflective mask blank 30 that ismanufactured, detection of a pseudo defect in defect inspection of thesurface of the protective film 22 using a highly sensitive defectinspection apparatus can be inhibited to further clarify a criticaldefect.

It is preferred that the protective film 22 be formed by ion beamsputtering in which an ion beam is radiated to a sputtering target of amaterial of the protective film 22. By the ion beam sputtering, thesurface of the protective film 22 can be smoothed, and thus, the surfaceof the absorber film 24 formed on the protective film 22, and further, asurface of the etching mask film 25 formed on the absorber film 24 canbe smoothed.

It is preferred that the method of manufacturing the reflective maskblank 30 according to this invention further include a step of formingthe etching mask film 25 arranged so as to be in contact with thesurface of the absorber film 24. By forming the etching mask film 25having dry etching characteristics that are different from those of theabsorber film 24, the transfer pattern formed in the absorber film 24can be highly accurate.

[Reflective Mask 40]

Next, the reflective mask 40 according to an embodiment of thisinvention is described below. FIG. 6 is a schematic view forillustrating the reflective mask 40 of this embodiment.

The reflective mask 40 according to this invention has a structure inwhich the absorber film 24 in the reflective mask blank 30 describedabove is patterned to form the absorber pattern 27 on the multilayerreflective film 21 or on the protective film 22. In the reflective mask40 according to this embodiment, when exposure is performed withexposure light such as EUV light, the exposure light is absorbed byportions of the surface of the reflective mask 40 on which the absorberfilm 24 is formed and the exposure light is reflected by the exposedprotective film 22 and multilayer reflective film 21 at other portionson which the absorber film 24 is removed, and thus, the reflective mask40 according to this embodiment can be used as the reflective mask 40for lithography. By using the reflective mask 40 according to thisinvention, when the reflective mask 40 is inspected and measured by adefect inspection apparatus, a coordinate measuring machine, and thelike, slippage of the back surface conductive film when the substrateand the like are fixed by a mount can be inhibited.

[Method of Manufacturing Semiconductor Device]

By transferring a transfer pattern such as a circuit pattern based onthe absorber pattern 27 of the reflective mask 40 to a resist filmformed on a transfer target such as a semiconductor substrate in alithography process using the reflective mask 40 described above and anexposure apparatus, and by various other steps, a semiconductor devicein which various transfer patterns and the like are formed on the objectto which transfer is performed such as a semiconductor substrate can bemanufactured.

According to a method of manufacturing a semiconductor device of thisinvention, the reflective mask 40 without a critical defect such as aforeign matter or a flaw can be used in defect inspection using a highlysensitive defect inspection apparatus, and thus, the transfer patternsuch as a circuit pattern that is transferred to a resist film formed onthe object to which transfer is performed such as a semiconductorsubstrate has no defect, and a semiconductor device having a fine andhighly accurate transfer pattern can be manufactured.

Note that, a fiducial mark 44 can be formed on the substrate 10 for amask blank, the substrate 20 provided with a multilayer reflective film,and the reflective mask blank 30 described above, and positions of thefiducial mark 44 and of a critical defect detected by the highlysensitive defect inspection apparatus can be controlled based oncoordinates thereof. Based on positional information of the criticaldefect (defect data) obtained, by correcting drawing data when thereflective mask 40 is manufactured so that the absorber pattern 27 isformed at a location where the critical defect exists based on theabove-mentioned defect data and transferred pattern (circuit pattern)data, defects can be reduced.

EXAMPLES

Examples of manufacturing the substrate 20 provided with a multilayerreflective film for EUV exposure, the reflective mask blank 30, and thereflective mask 40 according to this invention are described below.

First, the multilayer reflective film 21 was formed on the surface ofthe substrate 10 for a mask blank for EUV exposure as described below tomanufacture the substrate 20 provided with a multilayer reflective filmof Examples 1 to 5 and Comparative Examples 1 and 2.

<Manufacture of Substrate 10 for Mask Blank>

The substrate 10 for a mask blank used in Examples 1 to 5 andComparative Examples 1 and 2 was manufactured as described below.

As the substrate 10 for a mask blank, a SiO₂—TiO₂-based glass substratesized to be 152 mm×152 mm and having a thickness of 6.35 mm wasprepared. After front and back surfaces of the glass substrate werepolished in stages with cerium oxide abrasive grain or colloidal silicaabrasive grain using a double side polisher, surface treatment wasapplied with a low concentration of hydrofluosilicic acid. The surfaceroughness of a surface of the glass substrate obtained by this wasmeasured with an atomic force microscope, and the root means squareroughness (Rms) was 0.5 nm.

A surface shape (surface geometry, flatness) and TTV (Total ThicknessVariation) of a region of 148 mm×148 mm of the front and back surfacesof the glass substrate were measured by a wavelength-shiftinterferometer using a wavelength-modulated laser. As a result, theflatness of the front and back surfaces of the glass substrate was 290nm (convex). The result of the measurement of the surface shape(flatness) of the front surface of the glass substrate was stored in acomputer as height information with respect to a certain reference levelfor each measurement point, and is compared with 50 nm as a referencevalue of the front surface flatness (convex) necessary for the glasssubstrate and with 50 nm as a reference value of the back surfaceflatness, and the difference (necessary removal amount) was computed bya computer.

Then, conditions of local surface treatment in accordance with thenecessary removal amount were set with regard to each of treatment spotshape regions in the glass substrate surfaces. A treatment volume of aspot per unit time was calculated in advance using a dummy substrate bytreating the dummy substrate spot by spot without moving the substratefor a predetermined period of time similarly to actual treatment, andthe shape was measured by the apparatus for measuring the surface shapesof the front and back surfaces. In accordance with the necessary removalamount obtained from spot information and surface shape information ofthe glass substrate, a scanning speed in raster scanning of the glasssubstrate was determined.

In accordance with the set treatment conditions, local surface treatmentprocessing was performed so that the flatness of the front and backsurfaces of the glass substrate was equal to or smaller than thereference value described above by magnetic viscoelastic fluid polishing(Magneto Rheological Finishing: MRF) treatment using a substratefinishing apparatus with a magnetic viscoelastic fluid to adjust thesurface shape. Note that, the magnetic viscoelastic fluid used in thiscase contained an iron component, and an alkaline aqueous solutioncontaining about 2 wt % of cerium oxide as a polishing agent was used aspolishing slurry. Then, after the glass substrate was soaked in acleaning bath having a hydrochloric acid aqueous solution at about a 10%concentration (temperature of about 25° C.) for about 10 minutes,rinsing with pure water and drying with isopropyl alcohol (IPA) wasperformed.

The surface shape (surface geometry, flatness) of the surfaces of theglass substrate obtained was measured. The flatness of the front andback surfaces was about 40 to 50 nm. Further, the surface roughness of asurface of the glass substrate in a region of 1 μm×1 μm at an arbitrarylocation in a transfer pattern formation region (132 mm×132 mm) wasmeasured with an atomic force microscope, and the root means squareroughness (Rms) was 0.37 nm. The state was rougher compared with thesurface roughness before the local surface treatment by MRF.

Therefore, both of the front and back surfaces of the glass substratewas polished using a double side polisher under polishing conditions inwhich the surface shape of the surface of the glass substrate wasmaintained or improved. Polishing conditions of the finishing polish wasas follows.

-   -   Processing liquid: alkaline aqueous solution (NaOH)+polishing        agent (concentration: about 2 wt %)    -   Polishing agent: colloidal silica, average particle diameter:        about 70 nm    -   Number of rotations of polishing plate: about 1 rpm to about 50        rpm    -   Processing pressure: about 0.1 kPa to about 10 kPa    -   Polishing time: about 1 min to about 10 min

After that, the glass substrate was washed with the alkaline aqueoussolution (NaOH). Thus, the substrate 10 for mask blank for EUV exposurewas obtained.

The flatness and the surface roughness of the front and back surfaces ofthe substrate 10 for a mask blank obtained were measured. The flatnessof the front and back surfaces was about 40 nm and the state beforeprocessing by the double side polisher was maintained or improved, whichwas satisfactory. Further, a region of 1 μm×1 μm at an arbitrarylocation in the transfer pattern formation region (132 mm×132 mm) of thesubstrate 10 for a mask blank obtained was measured with an atomic forcemicroscope, and the surface roughness had a root means square roughness(Rms) of 0.13 nm and a maximum height (Rmax) of 1.2 nm.

Note that, the method of locally treating the substrate 10 for a maskblank according to this invention is not limited to the magneticviscoelastic fluid polishing treatment described above. The treatingmethod may also be Gas Cluster Ion Beams (GCIB) or a treating methodusing local plasma.

As described above, the substrate 10 for a mask blank used in Examples 1to 5 and Comparative Examples 1 and 2 was manufactured.

<Manufacture of Multilayer Reflective Film 21>

The multilayer reflective film 21 of Examples 1 to 5 and ComparativeExamples 1 and 2 was formed as follows. Specifically, an Mo layer (lowrefractive index layer having a thickness of 2.8 nm) and a Si layer(high refractive index layer having a thickness of 4.2 nm) werealternately laminated (40 pairs of laminates) by ion beam sputteringusing an Mo target and a Si target to form the multilayer reflectivefilm 21 on the substrate 10 for a mask blank described above. When themultilayer reflective film 21 was formed by ion beam sputtering, anincident angle of sputtering particles of Mo and Si with respect to thenormal to the main surface of the substrate 10 for a mask blank in theion beam sputtering was 30 degrees, and a gas flow rate of the ionsources was 8 sccm.

After the multilayer reflective film 21 was formed, an Ru protectivefilm 22 (having a thickness of 2.5 nm) was further successively formedon the multilayer reflective film 21 by ion beam sputtering to form thesubstrate 20 provided with a multilayer reflective film. When the Ruprotective film 22 was formed by ion beam sputtering, an incident angleof sputtering particles of Ru with respect to the normal to the mainsurface of the substrate 10 was 40 degrees, and a gas flow rate of theion source was 8 sccm.

<Formation of Fiducial Mark 44>

Then, a cross-shaped fiducial mark 44 having a length of 550 μm wasformed by photolithography at predetermined positions at four cornersoutside the region of 132 mm×132 mm of the Ru protective film 22 and themultilayer reflective film 21 of Examples 1 to 5 and ComparativeExamples 1 and 2. First, a resist film was formed on a surface of the Ruprotective film 22, and a pattern of the predetermined fiducial mark 44was drawn and developed to form a resist pattern of the fiducial mark44. Then, by dry etching the Ru protective film 22 and the substrate 20provided with a multilayer reflective film with CIF₃ gas that was anF-based gas under a state in which the resist pattern was used as amask, the fiducial mark 44 was formed in the Ru protective film 22 andthe substrate 20 provided with a multilayer reflective film. After that,the resist pattern that became unnecessary was separated. FIG. 10 is anillustration of the reflective mask 40 having the fiducial mark 44.

<Manufacture of Absorber Film 24>

Then, the absorber film 24 was formed on the surface of the protectivefilm 22 of the substrate 20 provided with a multilayer reflective filmof Examples 1 to 5 and Comparative Examples 1 and 2 described above byDC magnetron sputtering. The absorber film 24 was the absorber film 24of laminated films of two layers of a TaBN film as an absorbing layerand a TaBO film as a low reflection layer. A method of forming theabsorber film 24 in Examples 1 to 5 and Comparative Examples 1 and 2 isas follows.

First, the TaBN film as the absorbing layer was formed on the surface ofthe protective film 22 of the substrate 20 provided with a multilayerreflective film described above by DC magnetron sputtering. The TaBNfilm was formed by reactive sputtering in an atmosphere of a gas mixtureof Ar gas and N₂ gas under a state in which the substrate 20 providedwith a multilayer reflective film was opposed to a TaB mixture-sinteredtarget (Ta:B=80:20 in atomic ratio). Table 1 shows film formationconditions such as flow rates of the Ar gas and the N₂ gas when the TaBNfilm was formed. After the film formation, element composition of theTaBN film was measured by X-ray photoelectron spectroscopy (XPS). Table1 shows, together with the thickness of the TaBN film, the elementcomposition of the TaBN film measured by XPS. Note that, a crystalstructure of the TaBN film was measured by X-ray diffractometer (XRD),and that turned out to be an amorphous structure.

Next, the TaBO film (low reflection layer) containing Ta, B, and O wasfurther formed on the TaBN film by DC magnetron sputtering. As in thecase of the TaBN film, which is a first layer, the TaBO film was formedby reactive sputtering in an atmosphere of a gas mixture of Ar gas andO₂ gas under a state in which the substrate 20 provided with amultilayer reflective film was opposed to the TaB mixture-sinteredtarget (Ta:B=80:20 in atomic ratio). Table 1 shows film formationconditions such as flow rates of the Ar gas and the O₂ gas when the TaBOfilm was formed. After the film formation, element composition of theTaBO film was measured by X-ray photoelectron spectroscopy (XPS). Table1 shows, together with the thickness of the TaBO film, the elementcomposition of the TaBO film measured by XPS. Note that, a crystalstructure of the TaBO film was measured by X-ray diffractometer (XRD),and that turned out to be an amorphous structure. As described above,the absorber film 24 (laminated film) of Examples 1 to 5 and ComparativeExamples 1 and 2 was formed.

TABLE 1 Absorbing Target material TaB mixture-sintered target layer(Ta:B = 80:20 in atomic ratio) Film forming gas Ar (sccm) 12.4 N₂ (sccm)6.0 Film composition (by XPS) TaBN layer Ta (at %) 74.7 B (at %) 12.1 N(at %) 13.2 Film thickness (nm) 56 Low Target material (same asabsorbing layer) reflection Film forming gas Ar (sccm) 57.0 layer O₂(sccm) 28.6 Film composition (by XPS) TaBO layer Ta (at %) 40.7 B (at %)6.3 O (at %) 53.0 Film thickness (nm) 14 Total film thickness (nm) 70

<Manufacture of Back Surface Conductive Film 23>

The back surface conductive film 23 was formed on the back surface ofthe substrate 20 provided with a multilayer reflective film of Examples1 to 5 and Comparative Examples 1 and 2, on which the multilayerreflective film 21 was not formed, by DC magnetron sputtering asfollows. In Table 2, the composition, thickness, and the like of theback surface conductive film 23 that was formed are shown.

<Manufacture of Back Surface Conductive Film 23 of Example 1>

The back surface conductive film 23 of Example 1 was formed as follows.Specifically, reactive sputtering was performed using a gas mixture ofAr gas (flow rate: 24 sccm) and N₂ gas (flow rate: 6 sccm) as a filmforming gas under a state in which a Cr target was opposed to the backsurface of the substrate 20 provided with a multilayer reflective film.Through adjustment of a period of time for forming the back surfaceconductive film 23, the back surface conductive film 23 of Example 1 hada thickness of 20 nm.

<Manufacture of Back Surface Conductive Film 23 of Example 2>

As the back surface conductive film 23 of Example 2, the back surfaceconductive film 23 including three layers of CrN/CrCN/CrON was formed bysputtering using an inline sputtering apparatus. First, a CrN filmhaving a thickness of 15 nm was formed by reactive sputtering using achromium target in an atmosphere of a gas mixture of argon (Ar) andnitrogen (N) (Ar: 72 vol %, N₂: 28 vol %, under a pressure of 0.3 Pa).Then, a CrC film having a thickness of 25 nm was formed by reactivesputtering using a chromium target in an atmosphere of a gas mixture ofargon and methane (Ar: 96.5 vol %, CH₄:3.5 vol %, under a pressure of0.3 Pa). Note that, the film formation was performed using an inlinesputtering apparatus, and thus, the CrC film contained N, and the filmwas actually a CrCN film. Finally, a CrON film having a thickness of 20nm was formed by reactive sputtering using a chromium target in anatmosphere of a gas mixture of argon and nitric oxide (Ar: 87.5 vol %,NO: 12.5 vol %, under a pressure of 0.3 Pa). A nitrogen content of theCrN film obtained was 20 at %, a carbon content of the CrC film (CrCNfilm) was 6 at %, and an oxygen content and a nitrogen content of theCrON film were 45 at % and 25 at %, respectively. Note that, the filmthicknesses described above were film thicknesses when a single layerwas formed. After the three layers of CrN/CrCN/CrON were formed, athickness of the entire three layers was measured to be 70 nm.

<Manufacture of Back Surface Conductive Film 23 of Example 3>

The back surface conductive film 23 of Example 3 was formed under thesame conditions as those of the back surface conductive film 23 ofExample 1 except that the thickness thereof was 50 nm through adjustmentof a period of time for the formation thereof.

<Manufacture of Back Surface Conductive Film 23 of Example 4>

The back surface conductive film of Example 4 was formed as follows.Specifically, reactive sputtering was performed using a gas mixture ofAr gas (flow rate: 48 sccm) and N₂ gas (flow rate: 6 sccm) as a filmforming gas under a state in which a Cr target was opposed to the backsurface of the substrate 20 provided with a multilayer reflective film.Through adjustment of a period of time for forming the back surfaceconductive film 23, the back surface conductive film 23 of Example 4 hada thickness of 200 nm.

<Manufacture of Back Surface Conductive Film 23 of Example 5>

The back surface conductive film 23 of Example 5 was formed as follows.Specifically, reactive sputtering was performed using a gas mixture ofXe gas (flow rate: 12 sccm) and N₂ gas (flow rate: 6 sccm) as a filmforming gas under a state in which a Ta target was opposed to the backsurface of the substrate 20 provided with a multilayer reflective film.Through adjustment of a period of time for forming the back surfaceconductive film 23, the back surface conductive film 23 of Example 5 hada thickness of 70 nm.

<Manufacture of Back Surface Conductive Film 23 of Comparative Example1>

The back surface conductive film 23 of Comparative Example 1 was formedunder the same conditions as those of the back surface conductive film23 of Example 1 except that the thickness thereof was 200 nm throughadjustment of a period of time for the formation thereof.

<Manufacture of Back Surface Conductive Film 23 of Comparative Example2>

The back surface conductive film 23 of Comparative Example 2 was formedunder the same conditions as those of the back surface conductive film23 of Example 1 and Comparative Example 1 described above except that amixture ratio of the film forming gas was such that Ar gas had a flowrate of 24 sccm and N₂ gas had a flow rate of 8 sccm. Further, throughadjustment of a period of time for forming the back surface conductivefilm 23, the back surface conductive film 23 of Comparative Example 2had a thickness of 20 nm.

As described above, the reflective mask blank 30 of Examples 1 to 5 andComparative Examples 1 and 2 was obtained.

TABLE 2 Comparative Comparative Example 1 Example 2 Example 1 Example 2Back surface conductive film CrN CrN/CrCN/CrON CrN CrN material Filmthickness (nm) 20 70 200 20 Rmax (nm) 1.53 8.15 17.7 1.26 Rms (nm) 0.1520.83 2.89 0.141 Ratio in bearing curve 258.065 46.893 10.979 275.86(BA₇₀-BA₃₀)/(BD₇₀-BD₃₀) (%/nm) Measurement accuracy of 2.4 2.2 2.1 8.0coordinates of pattern for evaluation (nm) Defect inspection of surface∘ ∘ x ∘ of back surface conductive film is enabled/disabled

TABLE 3 Example 3 Example 4 Example 5 Back surface CrN CrN TaNconductive film material Film thickness (nm) 50 200 70 Rmax (nm) 3.2714.8 2.84 Rms (nm) 0.355 1.432 0.343 Ratio in bearing curve 111.1 19.1111.1 (BA₇₀-BA₃₀)/(BD₇₀-BD₃₀) (%/nm) Measurement accuracy of 2.3 2.1 2.4coordinates of pattern for evaluation (nm) Defect inspection of surface∘ ∘ ∘ of back surface conductive film is enabled/disabled

<Measurement with Atomic Force Microscope>

A region of 1 μm×1 μm at an arbitrary location (specifically, at thecenter of the substrate having the back surface conductive film 23formed thereon, and a position at which the mount of a coordinatemeasuring machine abuts the back surface conductive film 23) of thesurface of the back surface conductive film 23 of the reflective maskblank 30 obtained as Examples 1 to 5 and Comparative Examples 1 and 2was measured with an atomic force microscope. In Table 2 and Table 3,values of the surface roughness (Rmax, Rms) obtained by measurement withan atomic force microscope and of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) (%/nm) whenthe bearing area of 30% is defined as BA₃₀, the bearing area of 70% isdefined as BA₇₀, and the bearing depths corresponding to the bearingareas of 30% and 70% are defined as BD₃₀ and BD₇₀, respectively, areshown. Note that, the values of the surface roughness (Rmax, Rms) and of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) shown in Table 2 and Table 3 are average valuesof measurements that were made ten times.

In FIG. 8, results of bearing curve measurement of Examples 1 and 2 areshown. In FIG. 9, results of bearing curve measurement of ComparativeExamples 1 and 2 are shown. In FIG. 8 and FIG. 9, the vertical axisdenotes the bearing area (%) and the horizontal axis denotes the bearingdepth (nm). For reference purposes, BA₇₀, BA₃₀, BD₇₀, and BD₃₀ in theresult of bearing curve measurement of Example 2 are shown in FIG. 8.

In the cases of Examples 1 and 2 shown in FIG. 8, the values of(BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) were 258.065 (%/nm) and 46.893 (%/nm),respectively, which were in the range of from 15 (%/nm) to 260 (%/nm).On the other hand, in the cases of Comparative Examples 1 and 2 shown inFIG. 9, the values of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) were 10.979 (%/nm) and275.86 (%/nm), respectively, which were outside the range of from 15(%/nm) to 260 (%/nm).

Further, in Example 3, the value of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) was 111.1(%/nm), in Example 4, the value of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) was 19.1(%/nm), and in Example 5, the value of (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) was 111.1(%/nm), which were in the range of from 15 (%/nm) to 260 (%/nm).

Further, as shown in Table 2 and Table 3, in a region of 1 μm×1 μm ofthe surface of the back surface conductive film 23 of Examples 1 to 5,the maximum height (Rmax) of the surface roughness obtained bymeasurement with an atomic force microscope was 1.3 nm or more and 15 nmor less. On the other hand, in a region of 1 μm×1 μm of the surface ofthe back surface conductive film 23 of Comparative Examples 1 and 2, themaximum height (Rmax) of the surface roughness obtained by measurementwith an atomic force microscope was outside the range of 1.3 nm or moreand 15 nm or less.

Then, the surface of the back surface conductive film 23 of Examples 1to 5 and Comparative Examples 1 and 2 obtained as described above wasinspected for a defect using a mask blanks defect inspection apparatus(MAGICS M1350) manufactured by Lasertec Corporation. Table 2 and Table 3show results of the defect inspection. In Table 2 and Table 3, “∘” meansthat the inspection was able to be made and “x” means that theinspection was not able to be made (the inspection was discontinued dueto an overflow of the number of detected defects). As is clear fromTable 2, in the case of Comparative Example 1, the number of detecteddefects was too large and an overflow was caused, and thus, the defectinspection was not able to be made. This suggests that, when the valueof (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) in the bearing curve was 10.979 (%/nm) andless than 20 (%/nm) as in the case of Comparative Example 1, the numberof detected apparent defects increased due to pseudo defects, and thus,measurement by a defect inspection apparatus was impossible.

FIG. 11 is a graph for showing a frequency distribution in which arelationship between the bearing depth (nm) of Example 1 and a frequency(%) thereof is plotted. The vertical axis (Hist.) of the graph denotesthe frequency (%) and the horizontal axis (Depth) denotes the bearingdepth (nm).

From the graph of FIG. 11, an absolute value of the bearing depth (BDM)(nm) corresponding to a midpoint of a full width at half maximum FWHM(in the example shown in FIG. 11, the dotted line on which the bearingdepth is (BD1+BD2)/2) and an absolute value (nm) of the bearing depthcorresponding to ½ of the maximum height (Rmax) (in the example shown inFIG. 11, shown as the straight line with “½Rmax” that is in parallelwith the vertical axis) were determined. As a result, the bearing depth(nm) corresponding to the midpoint of the full width at half maximumFWHM was 0.707 nm, and the absolute value (nm) of the bearing depthcorresponding to ½ of the maximum height (Rmax) was 0.77 nm. Therefore,it was confirmed that the surface of the CrN film of Example 1 had asurface geometry in which the absolute value of the bearing depthcorresponding to the midpoint of the full width at half maximum wassmaller than the absolute value of the bearing depth corresponding to ½of the maximum height (Rmax).

The number of defects of 0.2 μm or more was determined before thesurface of the back surface conductive film of Example 1 was chucked byan electrostatic chuck and after the chucking and dechucking wererepeated five times by using a defect inspection apparatus (MAGICS 1350manufactured by Lasertec Corporation), and increase in the number wasdetermined. The measurement region was a region of 132 mm×132 mm at thecenter of the back surface conductive film. As a result, the increase inthe number of defects was 54, which was less than 100, and asatisfactory result was obtained.

Then, the surface of the back surface conductive film of Example 1 afterthe chucking and dechucking were repeated five times was cleaned with analkaline cleaning liquid. The number of defects of 0.2 μm or more wasreduced to 7, and a satisfactory surface state was able to be obtained.

Then, with regard to Example 2 and Example 5, similarly, the absolutevalue of the bearing depth (nm) corresponding to the midpoint of thefull width at half maximum FWHM and the absolute value (nm) of thebearing depth corresponding to ½ of the maximum height (Rmax) weredetermined. As a result, in the case of Example 2, the bearing depth(nm) corresponding to the midpoint of the full width at half maximumFWHM was 5.10 nm, and the absolute value (nm) of the bearing depthcorresponding to ½ of the maximum height (Rmax) was 4.08 nm. On theother hand, in the case of Example 5, the bearing depth (nm)corresponding to the midpoint of the full width at half maximum FWHM was1.42 nm, and the absolute value (nm) of the bearing depth correspondingto ½ of the maximum height (Rmax) was 1.42 nm. Therefore, it wasconfirmed that each of the surface of the CrN film of Example 2 and thesurface of the TaN film of Example 5 had a surface geometry in which theabsolute value of the bearing depth corresponding to the midpoint of thefull width at half maximum was equal to or larger than the absolutevalue of the bearing depth corresponding to ½ of the maximum height(Rmax).

The number of defects of 0.2 μm or more was determined before each ofthe surfaces of the back surface conductive films of Example 2 andExample 5 was chucked by an electrostatic chuck and after the chuckingand dechucking were repeated five times by using a defect inspectionapparatus (MAGICS 1350 manufactured by Lasertec Corporation), andincrease in the number was determined. The measurement region was aregion of 132 mm×132 mm at the center of the back surface conductivefilm. As a result, the increase in the number of defects was 788 inExample 2 and the increase in the number of defects was 176 in Example5, which were each more than 100.

However, when each of the surfaces of the back surface conductive filmsof Example 2 and Example 5 after the chucking and dechucking wererepeated five times was cleaned with an alkaline cleaning liquid, thenumber of defects of 0.2 μm or more was reduced to 23 in Example 2 andreduced to 11 in Example 5, and a satisfactory surface state was able tobe obtained.

<Manufacture of Mask 40 for Evaluating Coordinate Measurement>

A resist was applied to the surface of the absorber film 24 of thereflective mask blank 30 of Examples 1 to 5 and Comparative Examples 1and 2 by spin coating, and, through heating and cooling steps, a resistfilm having a thickness of 150 nm was formed. Then, a resist pattern wasformed through steps of drawing and developing a pattern 42 forevaluating coordinate measurement (simply referred to as “evaluationpattern 42”) illustrated in FIG. 10.

FIG. 10 is an illustration of the reflective mask 40 (mask 40 forevaluating coordinate measurement) having the evaluation pattern 42. Inthe reflective mask 40 illustrated in FIG. 10, 20×20 (400 in total)holes of the evaluation pattern 42 (hole pattern 42, the holes being inthe shape of a square having a side of 500 nm) were equidistantly formedin the region of 132 mm×132 mm in the absorber film 24. Note that, asillustrated in FIG. 10, the cross-shaped fiducial mark 44 (having alength of 550 μm) described above was formed at the four corners outsidethe region of 132 mm×132 mm.

Specifically, for the purpose of manufacturing the mask 40 forevaluating coordinate measurement, first, a coordinate measuring machine(IPRO manufactured by KLA-Tencor Corporation) was used to measurecoordinates of the fiducial marks 44 (intersections of the crosses)formed in the reflective mask blank 30. Then, a resist liquid wasapplied onto the absorber film 24 of the reflective mask blank 30 toform a resist film. Then, the evaluation pattern 42 described above wasdrawn using an electron beam (EB lithography) on the resist film anddevelopment was performed to form a resist pattern. In the electron beamlithography of the evaluation pattern 42, the fiducial marks 44described above were formed also in the absorber film 24 and the resistfilm formed on the multilayer reflective film 21. The fiducial marks 44were detected by the EB, and a correlation between coordinates of thefiducial marks 44 and of the evaluation pattern 42 was examined.Reference coordinates of the fiducial marks 44 were intersections of thecrosses of the fiducial marks 44. Then, the absorber film 24 was dryetched using a Cl-based gas (for example, a gas mixture of chlorine(Cl₂) and oxygen (O₂)) with the resist pattern being used as a mask toform the absorber pattern 27. Finally, the resist film was separated toobtain the mask 40 for evaluating coordinate measurement.

<Method of Evaluating Measurement Accuracy of Evaluation Pattern 42>

After the coordinates of the fiducial marks 44 of the mask 40 forevaluating coordinate measurement were measured using a coordinatemeasuring machine (IPRO manufactured by KLA-Tencor Corporation),coordinates of the evaluation pattern 42 were measured to measuremeasurement accuracy of the evaluation pattern 42 (coordinates of thehole pattern 42). In Table 2 and Table 3, measurement accuracy of theevaluation pattern 42 obtained by the measurement is shown. As is clearfrom Table 2 and Table 3, in the case of Comparative Example 2, themeasurement accuracy of the evaluation pattern 42 was 8.0 nm, which waslarger than those in Examples 1 to 5. This suggests that, when the valueof (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) in the bearing curve was 275.86 (%/nm) andmore than 260 (%/nm) as in the case of Comparative Example 2, slippageof the mask for evaluation was caused in the measurement using thecoordinate measuring machine to lower the positional accuracy of theevaluation pattern 42.

<Manufacture of Reflective Mask 40 and Manufacture of SemiconductorDevice>

A resist was applied to the surface of the absorber film 24 of thereflective mask blank 30 of Examples 1 to 5 and Comparative Examples 1and 2 by spin coating, and, through heating and cooling steps, a resistfilm having a thickness of 150 nm was formed. Then, a resist pattern wasformed through steps of drawing and developing a desired pattern. Theabsorber film 24 was patterned by predetermined dry etching with theresist pattern being used as a mask to form the absorber pattern 27 onthe protective film 22. Note that, when the absorber film 24 is a TaBNfilm, dry etching can be performed using a gas mixture of Cl₂ and He.Further, when the absorber film is a laminated film of two layers of aTaBN film and a TaBO film, the dry etching can be performed using a gasmixture of chlorine (Cl₂) and oxygen (O₂) (mixture ratio (flow rateratio) of chlorine (Cl₂):oxygen (O₂)=8:2).

After that, the resist film was removed, and cleaning with a chemicalsolution was performed similarly to the above, to thereby manufacturethe reflective mask 40 of Examples 1 to 5 and Comparative Examples 1 and2. Note that, in the drawing step described above, in accordance withdefect data prepared based on the fiducial marks, drawing data wascorrected so that the absorber pattern 27 was arranged at a location atwhich a critical defect exists based on the defect data and thetransferred pattern (circuit pattern) data, to thereby manufacture thereflective mask 40. The obtained reflective mask 40 of Examples 1 to 5and Comparative Examples 1 and 2 was inspected for a defect using ahighly sensitive defect inspection apparatus (“Teron 610” manufacturedby KLA-Tencor Corporation).

Slippage of the back surface conductive film due to a mount of thecoordinate measuring machine was inhibited, and the positional accuracywhen the pattern was measured using a coordinate measuring machine wassatisfactory. Thus, in measurement of the reflective mask 40 of Examples1 to 5 using a highly sensitive defect inspection apparatus, the numberof defects was small and practically no problem was presented. On theother hand, in the case of the reflective mask 40 of ComparativeExamples 1 and 2, slippage of the back surface conductive film due tothe mount of the coordinate measuring machine lowered the positionalaccuracy when the pattern was measured using the coordinate measuringmachine. Thus, a large number of defects were detected throughmeasurement using a highly sensitive defect inspection apparatus.

Then, with use of the reflective mask 40 of Examples 1 to 5 and anexposure apparatus, a pattern was transferred to a resist film formed ona transfer target that was a semiconductor substrate, and after that, awiring layer was patterned and a semiconductor device was manufactured.A semiconductor device without a pattern defect was able to bemanufactured.

Note that, in manufacturing the substrate 20 provided with a multilayerreflective film and the reflective mask blank 30 described above, afterthe multilayer reflective film 21 and the protective film 22 were formedon the main surface of the substrate 10 for a mask blank on the side onwhich the transfer pattern was to be formed, the back surface conductivefilm 23 was formed on the back surface on the opposite side of the mainsurface, but this invention is not limited thereto. After the backsurface conductive film 23 is formed on the main surface of the oppositeside to the main surface on the side on which the transfer pattern ofthe substrate 10 for a mask blank is to be formed to prepare theconductive film coated substrate, the multilayer reflective film 21, andfurther, the protective film 22 may be formed on the main surface on theside on which the transfer pattern is to be formed to manufacture thesubstrate 20 provided with a multilayer reflective film, and theabsorber film 24 may be further formed on the protective film 22 tomanufacture the reflective mask blank 30. In the case of the reflectivemask blank 30 manufactured by this method, the number of defects on thesurface of the back surface conductive film was slightly larger thanthat in examples described above, but the measurement accuracy of thecoordinates of the evaluation pattern was 2.5 nm or less, and it wasconfirmed that an effect similar to that of the examples described abovewas able to be obtained. When defect inspection is made under a state inwhich a mount of a defect inspection apparatus abuts the back surfaceconductive film 23 of the substrate 20 provided with a multilayerreflective film or the reflective mask blank 30, the positional accuracyof a detected defect in defect inspection of the substrate 20 providedwith a multilayer reflective film and the reflective mask blank 30 isalso improved, which is preferred.

In the above, the invention made by the inventors of this invention hasbeen described by way of the embodiments, but this invention is notlimited to the above-mentioned embodiments, and it should be understoodthat various changes are possible within the scope not departing fromthe gist of this invention.

This application claims priority from Japanese Patent Application No.2013-202494, filed on Sep. 27, 2013, the entire disclosure of which isincorporated herein.

DESCRIPTION OF REFERENCE NUMERALS

10 substrate for mask blank

20 substrate provided with multilayer reflective film

21 multilayer reflective film

22 protective film

23 back surface conductive film

24 absorber film

25 etching mask film

26 multilayer firm for mask blank

27 absorber pattern

30 reflective mask blank

40 reflective mask (mask for evaluating coordinate measurement)

42 evaluation pattern (hole pattern)

44 fiducial mark

50 substrate provided with conductive film.

The invention claimed is:
 1. A conductive film coated substratecomprising: a substrate for a mask blank for use in lithography; and aconductive film formed on one main surface of the substrate; wherein: ina relationship between a bearing area (%) and a bearing depth (nm) thatare obtained by measuring, with an atomic force microscope, a region of1 μm×1 μm of a surface of the conductive film, when a bearing area of30% is defined as BA₃₀, a bearing area of 70% is defined as BA₇₀, andbearing depths corresponding to the bearing areas of 30% and 70% aredefined as BD₃₀ and BD₇₀, respectively, the surface of the conductivefilm satisfies a relationship that (BA₇₀−BA₃₀)/(BD₇₀−BD₃₀) is 15 or moreand 260 or less (%/nm), and a maximum height (Rmax) is 1.3 nm or moreand 15 nm or less.
 2. A conductive film coated substrate according toclaim 1, wherein, in a frequency distribution chart where a relationshipbetween the bearing depth obtained by measuring with the atomic forcemicroscope and a frequency (%) of the obtained bearing depth of thesurface of the conductive film is plotted, an absolute value of abearing depth corresponding to a center of a full width at half maximum,which is determined from an approximated curve drawn through the plottedpoints or a highest frequency of the plotted points, is smaller than anabsolute value of a bearing depth corresponding to ½ of the maximumheight (Rmax) of surface roughness of the surface of the conductivefilm.
 3. A conductive film coated substrate according to claim 1,wherein, in a frequency distribution chart where a relationship betweenthe bearing depth obtained by measuring with the atomic force microscopeand a frequency (%) of the obtained bearing depth of the surface of theconductive film is plotted, an absolute value of a bearing depthcorresponding to a center of a full width at half maximum, which isdetermined from an approximated curve drawn through the plotted pointsor a highest frequency of the plotted points, is equal to or larger thanan absolute value of a bearing depth corresponding to ½ of the maximumheight (Rmax) of surface roughness of the surface of the conductivefilm.
 4. A multilayer reflective film coated substrate comprising amultilayer reflective film formed by alternately laminating a highrefractive index layer and a low refractive index layer, wherein themulti-layer reflection film is formed on a main surface of theconductive film coated substrate according to claim 1 on a side oppositeto a side on which the conductive film is formed.
 5. A multilayerreflective film coated substrate according to claim 4, furthercomprising a protective film formed on the multilayer reflective film.6. A reflective mask blank comprisingan absorber film formed on themultilayer reflective film of the multilayer reflective film coatedsubstrate according to claim
 4. 7. A reflective mask comprising anabsorber pattern provided on the multilayer reflective film, wherein theabsorber pattern is formed by patterning the absorber film of thereflective mask blank according to claim
 6. 8. A method of manufacturinga semiconductor device, comprising a step of performing a lithographyprocess with the reflective mask according to claim 7 using an exposureapparatus to form a transfer pattern on a transfer target.
 9. Areflective mask blank comprising an absorber film formed on theprotective film of the multilayer reflective film coated substrateaccording to claim
 5. 10. A reflective mask comprising an absorberpattern provided on the protective film, wherein the absorber pattern isformed by patterning the absorber film of the reflective mask blankaccording to claim
 9. 11. A method of manufacturing a semiconductordevice, comprising a step of performing a lithography process with thereflective mask according to claim 10 using an exposure apparatus toform a transfer pattern on a transfer target.